fix doxygen brief in subzero header files

src/IceSwitchLowering.cpp

 //===- subzero/src/IceSwitchLowering.cpp - Switch lowering ----------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file implements platform independent analysis of switch cases to
-/// improve the generated code.
+/// \brief Implements platform independent analysis of switch cases to improve
+/// the generated code.
 ///
 //===----------------------------------------------------------------------===//
 #include "IceSwitchLowering.h"
 
 #include "IceCfgNode.h"
 #include "IceTargetLowering.h"
 
 #include <algorithm>
 
 namespace Ice {
@@ skipping 71 matching lines @@
 
 bool CaseCluster::tryAppend(const CaseCluster &New) {
   // Can only append ranges with the same target and are adjacent
   bool CanAppend = this->Target == New.Target && this->High + 1 == New.Low;
   if (CanAppend)
     this->High = New.High;
   return CanAppend;
 }
 
 } // end of namespace Ice