common.opt (fcx-limited-range): Add SetByCombined flag.

common.opt (fcx-limited-range): Add SetByCombined flag.

	* common.opt (fcx-limited-range): Add SetByCombined flag.
	(ffinite-math-only, fmath-errno, frounding-math): Likewise.
	(fsignaling-nans, fsigned-zeros, ftrapping-math): Likewise.
	(fassociative-math, freciprocal-math): Likewise.
	(funsafe-math-optimizations): Likewise.
	* opth-gen.awk: Handle SetByCombined.
	* optc-gen.awk: Likewise.
	* opts.c (set_fast_math_flags): Don't override flag if set by
	frontend.
	(set_unsafe_math_optimizations_flags): Likewise.
	* doc/options.texi (Option properties): Document SetByCombined.

From-SVN: r169930