Doxygenize the documentation comments

There were many // comment used to document classes, functions etc. but
those are not picked up by doxygen which expects /// comments. This
converts many comments from // to /// in order to improve the generated
documentation.

BUG=
R=jvoung@chromium.org, kschimpf@google.com

Review URL: https://codereview.chromium.org/1216963007.

src/IceInstX8632.cpp

diff --git a/src/IceInstX8632.cpp b/src/IceInstX8632.cpp
index 2866430..fd33c55 100644
--- a/src/IceInstX8632.cpp
+++ b/src/IceInstX8632.cpp
@@ -6,10 +6,11 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This file implements the InstX8632 and OperandX8632 classes,
-// primarily the constructors and the dump()/emit() methods.
-//
+///
+/// \file
+/// This file implements the InstX8632 and OperandX8632 classes,
+/// primarily the constructors and the dump()/emit() methods.
+///
 //===----------------------------------------------------------------------===//
 
 #include "IceInstX8632.h"