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

[dominiq at lps dot ens.fr]

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

--- Comment #4 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2012-01-19 
20:27:50 UTC ---
On x86_64-darwin10 (Xcode 3.2.6) r183290 is OK.
On powerpc-apple-darwin9 (Xcode 3.1.4) 183218 is OK.