jit: Add checking for dereference of void *

jit: Add checking for dereference of void *

gcc/jit/ChangeLog:
	* jit-recording.h (gcc::jit::recording::type::is_void): New
	virtual function.
	(gcc::jit::recording::memento_of_get_type::is_void): New
	function, overriding default implementation.
	* libgccjit.c (gcc_jit_rvalue_dereference): Verify that
	the underlying type is not "void".

gcc/testsuite/ChangeLog:
	* jit.dg/test-error-dereferencing-void-ptr.c: New test case.

From-SVN: r219333