analyzer: detect and analyze virtual function calls

2021-08-15  Ankur Saini  <arsenic@sourceware.org>

gcc/analyzer/ChangeLog:
	PR analyzer/97114
	* region-model.cc (region_model::get_rvalue_1): Add case for
	OBJ_TYPE_REF.

gcc/testsuite/ChangeLog:
	PR analyzer/97114
	* g++.dg/analyzer/vfunc-2.C: New test.
	* g++.dg/analyzer/vfunc-3.C: New test.
	* g++.dg/analyzer/vfunc-4.C: New test.
	* g++.dg/analyzer/vfunc-5.C: New test.