re PR c++/50810 (c++0x-compat does not warn about narrowing conversions)

	PR c++/50810
gcc/c-family
	* c-opts.c (c_common_handle_option): Enable -Wnarrowing as part
	of -Wall; include -Wnarrowing in -Wc++0x-compat; adjust default
	Wnarrowing for C++0x and C++98.
	* c.opt ([Wnarrowing]): Update.
gcc/cp
	* typeck2.c (check_narrowing): Adjust OPT_Wnarrowing diagnostics.
	(digest_init_r): Call check_narrowing irrespective of the C++ dialect.
	* decl.c (check_initializer): Likewise.
	* semantics.c (finish_compound_literal): Likewise.
gcc/
	* configure.ac: Add -Wno-narrowing to warning options.
libcpp/
	* configure.ac: Add -Wno-narrowing to warning options.

From-SVN: r180794