svn rev #20685: trunk/src/

[raeburn@MIT.EDU]

Commit By: raeburn
Log Message: 
New macro for testing whether the compiler supports a given
command-line flag or not, and adding it to CFLAGS only if supported.
Use it for GCC flag -Wno-format-zero-length, which we were testing for
before, and for some additional flags: -Woverflow -Wstrict-overflow
-Wmissing-format-attribute -Werror=declaration-after-statement
-Wdeclaration-after-statement -Werror=variadic-macros
-Wvariadic-macros.  (The last few are because we've had some code
contributions that assumed full C99 support, and our baseline is
currently C89+, so if possible we want certain newer constructs
flagged as errors.)


Changed Files:
U   trunk/src/aclocal.m4