fix doxygen brief in subzero header files

src/IceInstX8632.h

 //===- subzero/src/IceInstX8632.h - x86-32 machine instructions -*- 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 used to house all the X8632 instructions. Subzero has been
-/// modified to use templates for X86 instructions, so all those definitions are
-/// are in IceInstX86Base.h
+/// \brief Used to house all the X8632 instructions.
+///
+/// Subzero has been modified to use templates for X86 instructions, so all
+/// those definitions are are in IceInstX86Base.h
 ///
 /// When interacting with the X8632 target (which should only happen in the
 /// X8632 TargetLowering) clients have should use the Ice::X8632::Traits::Insts
 /// traits, which hides all the template verboseness behind a type alias.
 ///
 /// For example, to create an X8632 MOV Instruction, clients should do
 ///
 /// ::Ice::X8632::Traits::Insts::Mov::create
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICEINSTX8632_H
 #define SUBZERO_SRC_ICEINSTX8632_H
 
 #include "IceDefs.h"
 #include "IceInst.h"
 #include "IceInstX86Base.h"
 #include "IceOperand.h"
 #include "IceTargetLoweringX8632Traits.h"
 
 #endif // SUBZERO_SRC_ICEINSTX8632_H