Unbreak the MSVC build, using namespace clang is required otherwise MSVC will not find raw_ostream.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135853 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Compilation.cpp b/lib/Driver/Compilation.cpp
index df07f78..47ac175 100644
--- a/lib/Driver/Compilation.cpp
+++ b/lib/Driver/Compilation.cpp
@@ -20,7 +20,9 @@
 #include "llvm/Support/Program.h"
 #include <sys/stat.h>
 #include <errno.h>
+
 using namespace clang::driver;
+using namespace clang;
 
 Compilation::Compilation(const Driver &D, const ToolChain &_DefaultToolChain,
                          InputArgList *_Args, DerivedArgList *_TranslatedArgs)