When working on something else, I noticed that failing to provide the
second argument to the static_assert operator would lead to an ICE.

Fixed thus, and tested against trunk on x86_64-unknown-linux-gnu.

gcc/cp/

	* semantics.c (finish_static_assert): Don't crash on erroneous
	message or condition.

gcc/testsuite/

	* g++.dg/cpp0x/static_assert8.C: New test.

From-SVN: r190182