c++: 'this' adjustment for devirtualized call

c++: 'this' adjustment for devirtualized call

My patch for 95719 made us do a better job of finding the actual virtual
function we want to call, but didn't update the 'this' pointer adjustment to
match.

	PR c++/100797
	PR c++/95719

gcc/cp/ChangeLog:

	* call.c (build_over_call): Adjust base_binfo in
	resolves_to_fixed_type_p case.

gcc/testsuite/ChangeLog:

	* g++.dg/inherit/virtual15.C: New test.