Fix PR c++/42260 and ensure PR c++/45383 is fixed

gcc/cp/
	c++/42260
	* call.c (add_builtin_candidate): At this point the resulting type
	of an indirection operator should be complete.

gcc/testsuite/
	c++/42260
	c++/45383
	* g++.dg/conversion/cast2.C: New test.
	* g++.dg/conversion/cond4/C: Likewise. Ensures we don't regress on
	PR c++/45383

From-SVN: r167250