analyzer: fix infinite recursion false +ves [PR108935]

gcc/analyzer/ChangeLog:
	PR analyzer/108935
	* infinite-recursion.cc (contains_unknown_p): New.
	(sufficiently_different_region_binding_p): New function, splitting
	out inner loop from...
	(sufficiently_different_p): ...here.  Extend detection of unknown
	svalues to also include svalues that contain unknown.  Treat
	changes in frames below the entry to the recursion as being
	sufficiently different to reject being an infinite recursion.

gcc/testsuite/ChangeLog:
	PR analyzer/108935
	* gcc.dg/analyzer/infinite-recursion-pr108935-1.c: New test.
	* gcc.dg/analyzer/infinite-recursion-pr108935-1a.c: New test.
	* gcc.dg/analyzer/infinite-recursion-pr108935-2.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>