c++: noexcept and copy elision [PR109030]

c++: noexcept and copy elision [PR109030]

When processing a noexcept, constructors aren't elided: build_over_call
has
	 /* It's unsafe to elide the constructor when handling
	    a noexcept-expression, it may evaluate to the wrong
	    value (c++/53025).  */
	 && (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.

	PR c++/109030

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_call_expression): Relax assert.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/noexcept77.C: New test.