Configure MODULESHOME location at installation time

[xdelaruelle]

As initially described on #287

Following a typical linux layout, e.g.

./configure \
		--prefix=/
		--etcdir=/etc \
		--initdir=/etc/modules/init \
		--modulefilesdir=/etc/modules/modulefiles
		--bindir=/usr/bin \
		--libdir=/usr/lib \
		--libexecdir=/usr/libexec \
		--datarootdir=/usr/share \
		--mandir=/usr/share/man \
		--docdir=/usr/share/doc \
		--vimdatadir=/usr/share/vim/vimfiles \

will lead to a wrong and empty MODULESHOMES (which seems not to be used by the tool itself, but is mainly used as $MODULESHOMES/init/<init-skript> by external scripts).

Suggested patches:

diff --git a/modulecmd.tcl.in b/modulecmd.tcl.in
index 843e178..8e77ec7 100644
--- a/modulecmd.tcl.in
+++ b/modulecmd.tcl.in
@@ -9066,7 +9066,7 @@ proc cmdModuleAutoinit {} {
    pushMode load
 
    # default MODULESHOME
-   setenv MODULESHOME @prefix@
+   setenv MODULESHOME [file dirname @initdir@]
 
    # register command location
    setenv MODULES_CMD [getAbsolutePath $::argv0]

Originally posted by @xdch47 in #287 (comment)

Without this fix, the prefix option is (from my point of view) is broken.

it feels pretty odd/wrong to have

./configure \
		--prefix=/usr/local/etc
		--etcdir=/etc \
		--initdir=/etc/modules/init \
		--modulefilesdir=/etc/modules/modulefiles
                ....

furthermore libdir, libexecdir,datarootdir,mandir,docdir,vimdatadir have to be manually prefix (with /usr/local) since they will be install to the wrong place (usr/local/etc) otherwise

an alternative to facilitate compability to all (but in my eyes stranges/broken setups) would be to add a --moduleshome option with the parentdir of the initdir as default.

Originally posted by @xdch47 in #287 (comment)

To clarify a bit more: the main compability I would like to keep is for users that had a local installation (default options -> /usr/local/Modules) and switch to a packaged installation.
However for a general packaging guideline is to have configuration files in /etc and binaries, libs, etc. in /usr …

Originally posted by @xdch47 in #287 (comment)

[xdelaruelle]

Will add a configuration option home that will control the setup of the MODULESHOME variable. And a ./configure option --with-moduleshome to enable the setup of the right value at installation time.