PR c++/87068 - missing diagnostic with fallthrough statement.

	* gimplify.c (expand_FALLTHROUGH_r): If IFN_FALLTHROUGH was found
	at the end of a seq, save its location to walk_stmt_info.
	(expand_FALLTHROUGH): Warn if IFN_FALLTHROUGH is at the end of
	a switch.

	* c-c++-common/Wimplicit-fallthrough-37.c: New test.

From-SVN: r269288