fix doxygen brief in subzero header files

src/IcePhiLoweringImpl.h

 //===------ subzero/src/IcePhiLoweringImpl.h - Phi lowering -----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This contains utilities for targets to lower Phis.
+/// \brief Utilities for targets to lower Phis.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICEPHILOWERINGIMPL_H
 #define SUBZERO_SRC_ICEPHILOWERINGIMPL_H
 
 #include "IceCfg.h"
 #include "IceCfgNode.h"
 #include "IceDefs.h"
 #include "IceInst.h"
@@ skipping 30 matching lines @@
       Node->getPhis().push_back(PhiHi);
       Phi->setDeleted();
     }
   }
 }
 
 } // end of namespace PhiLowering
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEPHILOWERINGIMPL_H