* acinclue.m4 (GLIBCPP_ENABLE_ATOMICITY): Handle IRIX.
	* aclocal.m4: Regenerated.
	* configure: Likewise.
	* config/os/irix/bits/atomicity.h: New file.
	* config/os/irix/bits/os_defines.h (_POSIX_SOURCE): Undefine.
	(__off_t): Define.
	(__off64_t): Likewise.
	(__ssize_t): Likewise.
	(_G_USING_THUNKS): Define to zero.

From-SVN: r37129