tweaks, recommend options(warn = 1) in tests

git-svn-id: https://svn.r-project.org/R/trunk@80032 00db46b3-68df-0310-9c12-caf00c1e9a41

doc/manual/R-exts.texi

@@ -5037,7 +5037,7 @@ ones.  But not all platforms use those CPUs, and not all@footnote{Not
 doing so is the default on Windows, overridden for the @R{} executables.
 It is also the default on some Solaris compilers.} which use them
 configure them to allow the use of extended precision.  In particular,
-32-bit ARM CPUs do not have extended precision nor long doubles, and
+current ARM CPUs do not have extended precision nor long doubles, and
 @command{clang} currently has long double the same as double on all ARM
 CPUs.  On the other hand some CPUs have higher-precision modes which may
 be used for @code{long double}, notably 64-bit PowerPC and Sparc.
@@ -5053,6 +5053,16 @@ mitigate the effects of extended-precision calculations.
 Tests which involve random inputs or non-deterministic algorithms should
 normally set a seed or be tested for many seeds.
 
+@item
+Tests should use @code{options(warn = 1)} as reporting
+
+@example
+There were 22 warnings (use warnings() to see them)
+@end example
+
+@noindent
+is pointless, especially for automated checking systems.
+
 @end itemize
 
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