chrono: (system_clock::is_steady): Update to N3291 from is_monotonic.

2011-07-20  Benjamin Kosnik  <bkoz@redhat.com>
	    Daniel Krugler  <daniel.kruegler@googlemail.com>

	* include/std/chrono: (system_clock::is_steady): Update to N3291
	from is_monotonic.
	(time_point): Add constexpr to nonmember arithmetic operators.
	* src/chrono.cc: Modify for above.
	* src/compatibility-c++0x.cc: Same.
	* testsuite/20_util/time_point/nonmember/constexpr.cc: New.
	* testsuite/20_util/time_point/1.cc: Modify.
	* testsuite/20_util/system_clock/constexpr_data.cc: Modify.
	* testsuite/20_util/system_clock/1.cc: Modify.
	* testsuite/20_util/monotonic_clock/constexpr_data.cc: Move to...
	* testsuite/20_util/steady_clock/constexpr_data.cc: ...here.
	* testsuite/30_threads/condition_variable/members/2.cc: Modify.
	* testsuite/30_threads/condition_variable_any/members/2.cc: Modify.

From-SVN: r176549