G M: A small patch to fix a couple of warnings in stdexcept.cpp for cl.exe which does not support #pragma visibility.

llvm-svn: 191988
diff --git a/libcxx/src/stdexcept.cpp b/libcxx/src/stdexcept.cpp
index 62c945a..9ef78aa 100644
--- a/libcxx/src/stdexcept.cpp
+++ b/libcxx/src/stdexcept.cpp
@@ -28,7 +28,9 @@
 
 // Note:  optimize for size
 
+#if ! defined(_LIBCPP_MSVC)
 #pragma GCC visibility push(hidden)
+#endif
 
 namespace
 {
@@ -91,7 +93,9 @@
 
 }
 
+#if ! defined(_LIBCPP_MSVC)
 #pragma GCC visibility pop
+#endif
 
 namespace std  // purposefully not using versioning namespace
 {