[Bug libstdc++/51906] thread lock test failures on darwin11 under Xcode 4.2

[iains at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51906

--- Comment #2 from Iain Sandoe <iains at gcc dot gnu.org> 2012-01-19 20:16:10 
UTC ---
not failing on
 *-darwin9 @r183184/r183270 (ppc/i686) 
[deallocate_global_thread errors remain present there, and not due to emutls
issues]
checking x86_64-darwin10, but was OK @ r182620.