re PR c++/54930 (Add warning switch for "returning reference to temporary" and similar)

re PR c++/54930 (Add warning switch for "returning reference to temporary" and similar)

gcc/c-family:
	PR c++/54930
	* c.opt (Wreturn_local_addr): Define new option.

gcc/c:
	PR c++/54930
	* c-typeck.c (c_finish_return): Use OPT_Wreturn_local_addr.

gcc/cp:
	PR c++/54930
	* typeck.c (maybe_warn_about_returning_address_of_local): Use
	OPT_Wreturn_local_addr.

gcc:
	PR c++/54930
	* doc/invoke.texi (Warning Options): Document -Wno-return-local-addr.

gcc/testsuite:
	PR c++/54930
	* gcc.dg/Wreturn-local-addr.c: New.
	* g++.dg/warn/Wno-return-local-addr.C: New.
	* g++.dg/warn/Wreturn-local-addr.C: New.

From-SVN: r192968