Quash a whole bunch of warnings

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@145624 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/cmath b/include/cmath
index ab67112..f0b985c 100644
--- a/include/cmath
+++ b/include/cmath
@@ -1600,7 +1600,7 @@
 using ::asinhl;
 using ::atanhl;
 using ::cbrtl;
-#endif !_MSC_VER
+#endif  // !_MSC_VER
 using ::copysignl;
 #ifndef _MSC_VER
 using ::erfl;