[PATCH] [libc++] Allow libc++ to be built on systems without POSIX threads

[Dan Albert]

I'm a little bit worried about the no-threads build bit-rotting (if any of us forget to wrap something in #ifndef _LIBCPP_HAS_NO_THREADS). Should we have a buildbot set up to build this configuration? Would it be possible to define noop implementations of all the things you've ifdef'd out so that we don't have to worry about that? It's possible that would make things more or a mess, but I'm not sure.

================
Comment at: src/condition_variable.cpp:19
@@ -14,2 +18,3 @@
 
+
 _LIBCPP_BEGIN_NAMESPACE_STD
----------------
nit

http://reviews.llvm.org/D3969