[c++0x] remove std::lock_error

[Benjamin Kosnik]

> std::lock_error was removed from the C++0x draft between n2691 and
> n2723, it's unused in libstdc++ except for
> testsuite/30_threads/headers/mutex/types_std_c++0x.cc but as its
> exported it needs to be kept for binary compatibility.

Sigh.

> 
>         * include/std/mutex: Move std::lock_error to ...
>         * src/mutex.cc: Here.

Should be:
src/compatibility.cc: Here.

Kill the doxygen markup too please.

>         * testsuite/30_threads/headers/mutex/types_std_c++0x.cc: Add
> checks for lock types and remove std::lock_error check.
> 
> tested x86_64 linux, is this OK for trunk?

With this change, yes.

thanks,
benjamin