re PR middle-end/68582 (-Wunused-function doesn't warn about unused static __attribute__((noreturn)) functions)

	PR middle-end/68582
	* cgraphunit.c (check_global_declaration): Only depend on TREE_THIS_VOLATILE
	for VAR_DECLs.

	* c-c++-common/pr68582.c: New test.

From-SVN: r231116