* 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