libgccjit: Allow sending a const pointer as argument

gcc/jit/ChangeLog:

	* jit-recording.h: Remove memento_of_get_const::accepts_writes_from,
	memento_of_get_type::is_same_type_as: new method.

gcc/testsuite/ChangeLog:

	* jit.dg/all-non-failing-tests.h: Add test-const-pointer-argument.c.
	* jit.dg/test-const-pointer-argument.c: New test.
3 files changed