re PR c++/85437 (member pointer static upcast rejected in a constexpr context)

	PR c++/85437
	PR c++/49171
	* cp-tree.h (REINTERPRET_CAST_P): New.
	* constexpr.c (cxx_eval_constant_expression) <case NOP_EXPR>:
	Reject REINTERPET_CAST_P conversions.  Use cplus_expand_constant
	for non-trivial PTRMEM_CST cases.
	* typeck.c (build_nop_reinterpret): New.
	(build_reinterpret_cast_1): Use it.  Set REINTERPRET_CAST_P on
	NOP_EXPRs returned by cp_convert.

	* g++.dg/cpp0x/addressof1.C: Make reinterpret cases runtime checks.
	* g++.dg/cpp0x/constexpr-cast.C: Remove xfails
	* g++.dg/cpp0x/constexpr-nullptr-2.C: Likewise.
	* g++.dg/cpp0x/constexpr-pmf1.C: Check when optimized.
	* g++.dg/cpp0x/pr85437-1.C: New.
	* g++.dg/cpp0x/pr85437-2.C: New.
	* g++.dg/cpp0x/pr85437-3.C: New.
	* g++.dg/cpp0x/pr85437-4.C: New.

From-SVN: r259629