PR c++/90825 - endless recursion when evaluating sizeof.

	PR c++/90825 - endless recursion when evaluating sizeof.
	PR c++/90832 - endless recursion when evaluating sizeof.
	* constexpr.c (cxx_eval_constant_expression): Don't recurse on the
	result of fold_sizeof_expr if is returns a SIZEOF_EXPR.
	* typeck.c (cxx_sizeof_expr): Only return a SIZEOF_EXPR if the operand
	is instantiation-dependent.

	* g++.dg/cpp0x/constexpr-sizeof2.C: New test.
	* g++.dg/cpp0x/constexpr-sizeof3.C: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@272221 138bc75d-0d04-0410-961f-82ee72b054a4