analyzer: fix ICE on 'bind' that returns a struct [PR107788]

gcc/analyzer/ChangeLog:
	PR analyzer/107788
	* region-model.cc (region_model::update_for_int_cst_return):
	Require that the return type be an integer type.
	(region_model::update_for_nonzero_return): Likewise.

gcc/testsuite/ChangeLog:
	PR analyzer/107788
	* g++.dg/analyzer/fd-bind-pr107783.C: New test.

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