PR debug/81278
	* tree-vrp.c (compare_assert_loc): Turn into a function template
	with stable template parameter.  Only test if a->e is NULL,
	!a->e == !b->e has been verified already.  Use e == NULL or
	e != NULL instead of e or ! e tests.  If stable is true, don't use
	iterative_hash_expr, on the other side allow a or b or both NULL
	and sort the NULLs last.
	(process_assert_insertions): Sort using compare_assert_loc<false>
	instead of compare_assert_loc, later sort using
	compare_assert_loc<true> before calling process_assert_insertions_for
	in a loop.  Use break instead of continue once seen NULL pointer.

From-SVN: r249975