tuple: Mark more constructors constexpr.

tuple: Mark more constructors constexpr.

2010-11-24  Benjamin Kosnik  <bkoz@redhat.com>

	* include/std/tuple: Mark more constructors constexpr.
	* include/bits/stl_pair.h: Same.
	* testsuite/20_util/tuple/requirements/dr801.cc: New.
	* testsuite/20_util/pair/requirements/dr801.cc: New.
	* testsuite/20_util/tuple/cons/constexpr.cc: Add cases for new
	constexpr constructors.
	* testsuite/20_util/pair/cons/constexpr.cc: Same.
	* testsuite/20_util/pair/comparison_operators/constexpr.cc: New.

	* testsuite/20_util/weak_ptr/comparison/cmp_neg.cc: Adjust line number.

From-SVN: r167118