Header guard canonicalization, clang part.

Modifications made by clang-tidy with minor tweaks.

llvm-svn: 215557
diff --git a/clang/lib/Driver/Tools.h b/clang/lib/Driver/Tools.h
index b248caa..b7330af 100644
--- a/clang/lib/Driver/Tools.h
+++ b/clang/lib/Driver/Tools.h
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef CLANG_LIB_DRIVER_TOOLS_H_
-#define CLANG_LIB_DRIVER_TOOLS_H_
+#ifndef LLVM_CLANG_LIB_DRIVER_TOOLS_H
+#define LLVM_CLANG_LIB_DRIVER_TOOLS_H
 
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/Types.h"
@@ -658,4 +658,4 @@
 } // end namespace driver
 } // end namespace clang
 
-#endif // CLANG_LIB_DRIVER_TOOLS_H_
+#endif