PATCH: Add threaded tests

[Benjamin Kosnik]

> 	* testsuite/thread/pthread1.cc: New test.
> 	* testsuite/thread/pthread2.cc: New test adapted from libstdc++/5347.
> 	* testsuite/thread/pthread3.cc: Likewise.
> 	* testsuite/thread/pthread4.cc: New test adapted from
> 	http://gcc.gnu.org/ml/gcc-bugs/2002-01/msg00679.html
> 	* testsuite/thread/pthread5.cc: New test adapted from libstdc++/5464.
> 	* testsuite/thread/pthread6.cc: New test adapted from libstdc++/5444.

Great! Thanks. I can confirm that this works as expected for me on linux 
with the single thread case.