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

[Joerg Sonnenberger]

I'm not sure I like the name _LIBCPP_SINGLE_THREADED, especially since it is pretty much exclusively used in the negative sense. Otherwise fine with me.

================
Comment at: sources/cxx-stl/llvm-libc++/libcxx/include/__config:124
@@ -121,1 +123,3 @@
 
+#if defined(_POSIX_THREADS) && _POSIX_THREADS > 0
+#  define _LIBCPP_SINGLE_THREADED 0
----------------
  #if _POSIX_THREADS - 0 > 0

might be simpler

http://reviews.llvm.org/D3969