re PR c++/22132 (Wrong code: upcasting a const class pointer to struct the class derives from (C/old-style cast))

	PR c++/22132
	* call.c (implicit_conversion): Add c_cast_p parameter.
	(standard_conversion): Likewise.  Allow conversions between
	differently-qualified pointer types when performing a C-style
	cast.
	(add_function_candidate): Adjust callee.
	(build_builtin_candidate): Likewise.
	(build_user_type_conversion_1): Likewise.
	(conditional_conversion): Likewise.
	(can_convert_arg): Likewise.
	(can_convert_arg_bad): Likewise.
	(perform_implicit_conversion): Likewise.
	* cp-tree.h (comp_ptr_ttypes_const): Declare.
	* typeck.c (comp_ptr_ttypes_const): Give it external linkage.
	Return bool.

	PR c++/22132
	* g++.dg/expr/cast4.C: New test.

From-SVN: r102059