jit: handle equality of function pointer types

jit: handle equality of function pointer types

gcc/jit/ChangeLog:
	* jit-recording.c
	(gcc::jit::recording::function_type::is_same_type_as): New function.
	* jit-recording.h: In namespace gcc::jit::recording::
	(type::accepts_writes_from): Use is_same_type_as rather than pointer
	equality.
	(type::is_same_type_as): New virtual function.
	(function_type::is_same_type_as): New override.

gcc/testsuite/ChangeLog:
	* jit.dg/test-error-mismatching-types-in-assignment-fn-ptr.c: New
	test case.
	* jit.dg/test-returning-function-ptr.c (create_code): Update to
	create a function pointer type independently of the call to
	gcc_jit_function_get_address, and assign the pointer to a local
	before returning it, to exercise the function pointer type
	comparison code.

From-SVN: r253255