analyzer: decls are not on the heap

analyzer: decls are not on the heap

Whilst debugging the remaining state explosion in PR analyzer/93355
I noticed that half of the states at an exploding program point had:
  'malloc': {'&buf': 'non-heap'}
whereas the other half didn't, presumably depending on whether the path
to each enode had used this local buffer:
  char buf[400];

This patch tweaks malloc_state_machine::get_default_state to be smarter
about this, so that we can implicitly treat pointers to decls as
non-heap, preventing pointless differences between sm_state_map
instances.  With that, all of the states in question have equal (empty)
malloc sm-state - though the state explosion continues for other reasons.

gcc/analyzer/ChangeLog:
	PR analyzer/93355
	* sm-malloc.cc (malloc_state_machine::get_default_state): Look at
	the base region when considering pointers.  Treat pointers to
	decls as being non-heap.