[PATCH] [libcxx] Set -D_LIBCPP_HAS_NO_THREADS and -D_LIBCPP_HAS_NO_MONOTONIC_CLOCK based on available_features

[Dan Albert]

================
Comment at: lit.cfg:361
@@ +360,3 @@
+
+        if 'no-monotonic-clock' in self.config.available_features:
+            self.compile_flags += ['-D_LIBCPP_HAS_NO_MONOTONIC_CLOCK']
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One nitpick: libcpp-has-no-monotonic-clock to match the other one?

http://reviews.llvm.org/D5214