Implement -fsanitize=vla-bound.

	* opts.c (common_handle_option): Handle vla-bound.
	* sanitizer.def (BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE):
	Define.
	* flag-types.h (enum sanitize_code): Add SANITIZE_VLA.
	* asan.c (initialize_sanitizer_builtins): Build BT_FN_VOID_PTR_PTR.
c-family/
	* c-ubsan.c: Don't include hash-table.h.
	(ubsan_instrument_vla): New function.
	* c-ubsan.h: Declare it.
cp/
	* decl.c (cp_finish_decl): Move C++1y bounds checking...
	(compute_array_index_type): ...here.  Add VLA instrumentation.
	Call stabilize_vla_size.
	(grokdeclarator): Don't call stabilize_vla_size here.
c/
	* c-decl.c (grokdeclarator): Add VLA instrumentation.
testsuite/
	* g++.dg/ubsan/cxx1y-vla.C: New test.
	* c-c++-common/ubsan/vla-3.c: New test.
	* c-c++-common/ubsan/vla-2.c: New test.
	* c-c++-common/ubsan/vla-4.c: New test.
	* c-c++-common/ubsan/vla-1.c: New test.

From-SVN: r204334