[v3] c++0x <mutex> and <condition_variable>

[Paolo Carlini]

.. Hint: if you want to convince yourself, on linux, that we are on the 
safe track vs these features, I suggest sabotaging the autconf tests for 
cstdint and for gthreads individually or both, in order to make sure the 
outcome is false, rebuild and run the testsuite. Since at this point we 
are rather confident that the tests themselves are accurate, we should 
be safe.

Paolo.