* common.opt (fsigned-zeros): New command line option.
* flags.h (HONOR_SIGNED_ZEROS): Control via flag_signed_zeros instead
of flag_unsafe_math_optimizations.
* opts.c (set_fast_math_flags): The -ffast-math command line option
implies -fno-signed-zeros.
(fast_math_flags_set_p): Likewise.
* doc/invoke.texi: Document new -fno-signed-zeros option, and update
the documentation of -ffast-math appropriately. Wrap long lines.
* gcc.dg/pr30172-1.c: Specify the -fno-signed-zeros command line
option instead of -funsafe-math-optimizations.
From-SVN: r120978
