fix doxygen brief in subzero header files

src/IceTimerTree.h

 //===- subzero/src/IceTimerTree.h - Pass timer defs -------------*- 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 the TimerTree class, which allows flat and cumulative
+/// \brief Declares the TimerTree class, which allows flat and cumulative
 /// execution time collection of call chains.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICETIMERTREE_H
 #define SUBZERO_SRC_ICETIMERTREE_H
 
 // TODO(jpp): Refactor IceDefs.
 #include "IceDefs.h"
 #include "IceTimerTree.def"
@@ skipping 67 matching lines @@
   std::vector<IceString> IDs;       /// indexed by TimerIdT
   std::vector<TimerTreeNode> Nodes; /// indexed by TTindex
   std::vector<double> LeafTimes;    /// indexed by TimerIdT
   std::vector<size_t> LeafCounts;   /// indexed by TimerIdT
   TTindex StackTop = 0;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETIMERTREE_H