Driver.cpp: Restore clang/Config/config.h to be included at last not to prevent llvm-config.h.

Or "llvm/Support/system_error.h" could not be compiled on mingw.

llvm-svn: 169354
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index cea24fd..a6410d8 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -11,7 +11,6 @@
 #include "InputInfo.h"
 #include "ToolChains.h"
 #include "clang/Basic/Version.h"
-#include "clang/Config/config.h"
 #include "clang/Driver/Action.h"
 #include "clang/Driver/Arg.h"
 #include "clang/Driver/ArgList.h"
@@ -34,6 +33,10 @@
 #include "llvm/Support/raw_ostream.h"
 #include <map>
 
+// FIXME: It would prevent to include llvm-config.h
+// if it were included before system_error.h.
+#include "clang/Config/config.h"
+
 using namespace clang::driver;
 using namespace clang;