fix doxygen brief in subzero header files

src/IceClFlagsExtra.h

 //===- subzero/src/IceClFlagsExtra.h - Extra Cl Flags -----------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file declares command line flags primarily used for non-minimal builds.
+/// \brief Declares command line flags primarily used for non-minimal builds.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICECLFLAGSEXTRA_H
 #define SUBZERO_SRC_ICECLFLAGSEXTRA_H
 
 #include "IceDefs.h"
 
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-parameter"
@@ skipping 55 matching lines @@
 
   IceString AppName = "";
   IceString IRFilename = "";
   IceString LogFilename = "";
   IceString OutputFilename = "";
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICECLFLAGSEXTRA_H