fix doxygen brief in subzero header files

src/IceCfgNode.cpp

 //===- subzero/src/IceCfgNode.cpp - Basic block (node) implementation -----===//
 //
 //                        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 the CfgNode class, including the complexities of
+/// \brief Implements the CfgNode class, including the complexities of
 /// instruction insertion and in-edge calculation.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "IceCfgNode.h"
 
 #include "IceAssembler.h"
 #include "IceCfg.h"
 #include "IceGlobalInits.h"
 #include "IceInst.h"
@@ skipping 1385 matching lines @@
   InstIntrinsicCall *Inst = InstIntrinsicCall::create(
       Func, 5, Func->makeVariable(IceType_i64), RMWI64Name, Info->Info);
   Inst->addArg(AtomicRMWOp);
   Inst->addArg(Counter);
   Inst->addArg(One);
   Inst->addArg(OrderAcquireRelease);
   Insts.push_front(Inst);
 }
 
 } // end of namespace Ice