re PR bootstrap/3456 (bootstrapping gcc-3.0 with threadmodel=posix fails on IRIX64...

re PR bootstrap/3456 (bootstrapping gcc-3.0 with threadmodel=posix fails on IRIX64 6.5)

	gcc:
	PR bootstrap/3456
	* config.gcc (mips-sgi-irix[56]*): Enable pthread support.
	* doc/install.texi (mips-sgi-irix6): pthread support works now.

	libstdc++-v3:
	PR bootstrap/3456
	* testsuite/22_locale/locale/cons/12658_thread-1.cc: Enable on
	mips-sgi-irix6*.
	* testsuite/22_locale/locale/cons/12658_thread-2.cc: Likewise.
	* testsuite/thread/18185.cc: Likewise.
	* testsuite/thread/pthread1.cc: Likewise.
	* testsuite/thread/pthread2.cc: Likewise.
	* testsuite/thread/pthread3.cc: Likewise.
	* testsuite/thread/pthread4.cc: Likewise.
	* testsuite/thread/pthread5.cc: Likewise.
	* testsuite/thread/pthread6.cc: Likewise.
	* testsuite/thread/pthread7-rope.cc: Likewise.
	* testsuite/tr1/2_general_utilities/shared_ptr/thread/default_weaktoshared.cc: Likewise.
	* testsuite/tr1/2_general_utilities/shared_ptr/thread/mutex_weaktoshared.cc: Likewise.

From-SVN: r126685