build: Use option groups in configure output

Minor edits to current build flags and its help texts as well
as grouping shared and i18n options into separate option groups.

Also, validate i18n default/logic similar to how we treat other
options. `--download` isn't really intl-specific but is only used
for that purpose which is why it's grouped similarly.

PR-URL: nodejs#1533
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Steven R. Loomis <srl@icu-project.org>

configure

@@ -31,6 +31,16 @@ valid_arm_float_abi = ('soft', 'softfp', 'hard')
 valid_mips_arch = ('loongson', 'r1', 'r2', 'r6', 'rx')
 valid_mips_fpu = ('fp32', 'fp64', 'fpxx')
 valid_mips_float_abi = ('soft', 'hard')
+valid_intl_modes = ('none', 'small-icu', 'full-icu', 'system-icu')
+
+# create option groups
+shared_optgroup = optparse.OptionGroup(parser, "Shared libraries",
+    "Flags that allows you to control whether you want to build against "
+    "built-in dependencies or its shared representations. If necessary, "
+    "provide multiple libraries with comma.")
+intl_optgroup = optparse.OptionGroup(parser, "Internationalization",
+    "Flags that lets you enable i18n features in io.js as well as which "
+    "library you want to build against.")
 
 # Options should be in alphabetical order but keep --prefix at the top,
 # that's arguably the one people will be looking for most.
@@ -78,90 +88,92 @@ parser.add_option("--openssl-no-asm",
     dest="openssl_no_asm",
     help="Do not build optimized assembly for OpenSSL")
 
-parser.add_option('--shared-http-parser',
+shared_optgroup.add_option('--shared-http-parser',
     action='store_true',
     dest='shared_http_parser',
     help='link to a shared http_parser DLL instead of static linking')
 
-parser.add_option('--shared-http-parser-includes',
+shared_optgroup.add_option('--shared-http-parser-includes',
     action='store',
     dest='shared_http_parser_includes',
     help='directory containing http_parser header files')
 
-parser.add_option('--shared-http-parser-libname',
+shared_optgroup.add_option('--shared-http-parser-libname',
     action='store',
     dest='shared_http_parser_libname',
     default='http_parser',
     help='alternative lib name to link to [default: %default]')
 
-parser.add_option('--shared-http-parser-libpath',
+shared_optgroup.add_option('--shared-http-parser-libpath',
     action='store',
     dest='shared_http_parser_libpath',
     help='a directory to search for the shared http_parser DLL')
 
-parser.add_option('--shared-libuv',
+shared_optgroup.add_option('--shared-libuv',
     action='store_true',
     dest='shared_libuv',
     help='link to a shared libuv DLL instead of static linking')
 
-parser.add_option('--shared-libuv-includes',
+shared_optgroup.add_option('--shared-libuv-includes',
     action='store',
     dest='shared_libuv_includes',
     help='directory containing libuv header files')
 
-parser.add_option('--shared-libuv-libname',
+shared_optgroup.add_option('--shared-libuv-libname',
     action='store',
     dest='shared_libuv_libname',
     default='uv',
     help='alternative lib name to link to [default: %default]')
 
-parser.add_option('--shared-libuv-libpath',
+shared_optgroup.add_option('--shared-libuv-libpath',
     action='store',
     dest='shared_libuv_libpath',
     help='a directory to search for the shared libuv DLL')
 
-parser.add_option('--shared-openssl',
+shared_optgroup.add_option('--shared-openssl',
     action='store_true',
     dest='shared_openssl',
     help='link to a shared OpenSSl DLL instead of static linking')
 
-parser.add_option('--shared-openssl-includes',
+shared_optgroup.add_option('--shared-openssl-includes',
     action='store',
     dest='shared_openssl_includes',
     help='directory containing OpenSSL header files')
 
-parser.add_option('--shared-openssl-libname',
+shared_optgroup.add_option('--shared-openssl-libname',
     action='store',
     dest='shared_openssl_libname',
     default='crypto,ssl',
     help='alternative lib name to link to [default: %default]')
 
-parser.add_option('--shared-openssl-libpath',
+shared_optgroup.add_option('--shared-openssl-libpath',
     action='store',
     dest='shared_openssl_libpath',
     help='a directory to search for the shared OpenSSL DLLs')
 
-parser.add_option('--shared-zlib',
+shared_optgroup.add_option('--shared-zlib',
     action='store_true',
     dest='shared_zlib',
     help='link to a shared zlib DLL instead of static linking')
 
-parser.add_option('--shared-zlib-includes',
+shared_optgroup.add_option('--shared-zlib-includes',
     action='store',
     dest='shared_zlib_includes',
     help='directory containing zlib header files')
 
-parser.add_option('--shared-zlib-libname',
+shared_optgroup.add_option('--shared-zlib-libname',
     action='store',
     dest='shared_zlib_libname',
     default='z',
     help='alternative lib name to link to [default: %default]')
 
-parser.add_option('--shared-zlib-libpath',
+shared_optgroup.add_option('--shared-zlib-libpath',
     action='store',
     dest='shared_zlib_libpath',
     help='a directory to search for the shared zlib DLL')
 
+parser.add_option_group(shared_optgroup)
+
 # TODO document when we've decided on what the tracing API and its options will
 # look like
 parser.add_option('--systemtap-includes',
@@ -225,33 +237,38 @@ parser.add_option('--with-etw',
     dest='with_etw',
     help='build with ETW (default is true on Windows)')
 
-parser.add_option('--download',
+parser.add_option('--with-intl',
     action='store',
-    dest='download_list',
-    help=nodedownload.help())
+    dest='with_intl',
+    default='none',
+    choices=valid_intl_modes,
+    help='Intl mode (valid choices: {0}) [default: %default]'.format(
+        ', '.join(valid_intl_modes)))
 
-parser.add_option('--with-icu-path',
+intl_optgroup.add_option('--with-icu-path',
     action='store',
     dest='with_icu_path',
     help='Path to icu.gyp (ICU i18n, Chromium version only.)')
 
-parser.add_option('--with-icu-locales',
+intl_optgroup.add_option('--with-icu-locales',
     action='store',
     dest='with_icu_locales',
     default='root,en',
     help='Comma-separated list of locales for "small-icu". "root" is assumed. '
         '[default: %default]')
 
-parser.add_option('--with-intl',
-    action='store',
-    dest='with_intl',
-    help='Intl mode: none, full-icu, small-icu [default: none]')
-
-parser.add_option('--with-icu-source',
+intl_optgroup.add_option('--with-icu-source',
     action='store',
     dest='with_icu_source',
     help='Intl mode: optional local path to icu/ dir, or path/URL of icu source archive.')
 
+intl_optgroup.add_option('--download',
+    action='store',
+    dest='download_list',
+    help=nodedownload.help())
+
+parser.add_option_group(intl_optgroup)
+
 parser.add_option('--with-perfctr',
     action='store_true',
     dest='with_perfctr',
@@ -812,7 +829,7 @@ def configure_intl(o):
   with_intl = options.with_intl
   with_icu_source = options.with_icu_source
   have_icu_path = bool(options.with_icu_path)
-  if have_icu_path and with_intl:
+  if have_icu_path and with_intl != 'none':
     print 'Error: Cannot specify both --with-icu-path and --with-intl'
     sys.exit(1)
   elif have_icu_path:
@@ -850,11 +867,6 @@ def configure_intl(o):
     # use the "system" .gyp
     o['variables']['icu_gyp_path'] = 'tools/icu/icu-system.gyp'
     return
-  else:
-    print 'Error: unknown value --with-intl=%s' % with_intl
-    sys.exit(1)
-  # Note: non-ICU implementations could use other 'with_intl'
-  # values.
 
   # this is just the 'deps' dir. Used for unpacking.
   icu_parent_path = os.path.join(root_dir, 'deps')