re PR c++/54532 ([C++0x][constexpr] internal error when initializing static constexpr with pointer to non-static member variable)

	PR c++/54532
	* expr.c (cplus_expand_constant): Do nothing if the class is
	incomplete.
	* semantics.c (reduced_constant_expression_p): Allow PTRMEM_CST.
	* typeck2.c (store_init_value): Use reduced_constant_expression_p.
	* decl.c (maybe_register_incomplete_var): Handle PTRMEM_CST.
	(complete_vars): Likewise.

From-SVN: r196852