re PR c++/84463 (Supposedly-incompliant "error: '* key0' is not a constant expression")

re PR c++/84463 (Supposedly-incompliant "error: '* key0' is not a constant expression")

	PR c++/84463
	* typeck.c (cp_build_addr_expr_1): Move handling of offsetof-like
	tricks from here to ...
	* cp-gimplify.c (cp_fold) <case ADDR_EXPR>: ... here.  Only use it
	if INDIRECT_REF's operand is INTEGER_CST cast to pointer type.

	* g++.dg/cpp0x/constexpr-nullptr-1.C: Add -O1 to dg-options.
	* g++.dg/cpp0x/constexpr-nullptr-2.C: Expect different diagnostics
	in two cases.  Uncomment two other tests and add expected dg-error for
	them.
	* g++.dg/init/struct2.C: Cast to int rather than long to avoid
	-Wnarrowing diagnostics on some targets for c++11.
	* g++.dg/parse/array-size2.C: Remove xfail.
	* g++.dg/cpp0x/constexpr-84463.C: New test.

From-SVN: r259458