PR middle-end/94004 - missing -Walloca on calls to alloca due to -Wno-system-headers

PR middle-end/94004 - missing -Walloca on calls to alloca due to -Wno-system-headers

gcc/testsuite/ChangeLog:

	PR middle-end/94004
	* gcc.dg/Walloca-larger-than-3.c: New test.
	* gcc.dg/Walloca-larger-than-3.h: New test header.
	* gcc.dg/Wvla-larger-than-4.c: New test.

gcc/ChangeLog:

	PR middle-end/94004
	* gimple-ssa-warn-alloca.c (pass_walloca::execute): Issue warnings
	even for alloca calls resulting from system macro expansion.
	Include inlining context in all warnings.