invoke.texi (-frename-registers): Add enabled at -O3.

invoke.texi (-frename-registers): Add enabled at -O3.

	* doc/invoke.texi (-frename-registers: Add enabled at -O3.
	(-fprofile-values): Add enabled with profile-{generate,use}.
	(-fvpt): Same.
	(-ftracer): Add enabled with profile-use.
	(-funit-at-a-time): Add enabled at -O2,-O3.
	(-funroll-loops): Add enabled with profile-use.
	(-funswitch-loops): Add enabled with profile-use.  Remove duplicates.
	(max-gcse-passes): Mention default.
	(max-cse-path-length): Mention default.

From-SVN: r79925