cp:
	PR c++/17431
	* call.c (standard_conversion): Add FLAGS parameter. Do not allow
	derived to base conversion when checking constructor
	accessibility.
	(implicit_conversion): Pass FLAGS to standard_conversion.
	(check_constructir_callable): Disallow conversion functions.
testsuite:
	PR c++/17431
	* g++.dg/overload/arg1.C: New.
	* g++.dg/overload/arg2.C: New.
	* g++.dg/overload/arg3.C: New.
	* g++.dg/overload/arg4.C: New.

From-SVN: r91559