Doxygenize the documentation comments

src/IceConditionCodesX8664.h

Index: src/IceConditionCodesX8664.h
diff --git a/src/IceConditionCodesX8664.h b/src/IceConditionCodesX8664.h
index ec30f88b0d880af8be3a42ff2508d68e2ba72751..06155eafcc68a90ef0556705b37b564969fbaaaa 100644
--- a/src/IceConditionCodesX8664.h
+++ b/src/IceConditionCodesX8664.h
@@ -6,9 +6,10 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This file declares the condition codes for x86-64.
-//
+///
+/// \file
+/// This file declares the condition codes for x86-64.
+///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICECONDITIONCODESX8664_H
@@ -20,8 +21,8 @@
 namespace Ice {
 
 class CondX8664 {
-  // An enum of condition codes used for branches and cmov. The enum value
-  // should match the value used to encode operands in binary instructions.
+  /// An enum of condition codes used for branches and cmov. The enum value
+  /// should match the value used to encode operands in binary instructions.
   enum BrCond {
 #define X(tag, encode, opp, dump, emit) tag encode,
     ICEINSTX8664BR_TABLE
@@ -29,9 +30,9 @@ class CondX8664 {
         Br_None
   };
 
-  // An enum of condition codes relevant to the CMPPS instruction. The enum
-  // value should match the value used to encode operands in binary
-  // instructions.
+  /// An enum of condition codes relevant to the CMPPS instruction. The enum
+  /// value should match the value used to encode operands in binary
+  /// instructions.
   enum CmppsCond {
 #define X(tag, emit) tag,
     ICEINSTX8664CMPPS_TABLE