Documentation cleanup: escape @ in a Doxygen comment.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158548 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/IdentifierTable.cpp b/lib/Basic/IdentifierTable.cpp
index c7e83f4..6981455 100644
--- a/lib/Basic/IdentifierTable.cpp
+++ b/lib/Basic/IdentifierTable.cpp
@@ -154,8 +154,8 @@
   Info.setIsCPlusPlusOperatorKeyword();
 }
 
-/// AddObjCKeyword - Register an Objective-C @keyword like "class" "selector" or
-/// "property".
+/// AddObjCKeyword - Register an Objective-C \@keyword like "class" "selector"
+/// or "property".
 static void AddObjCKeyword(StringRef Name,
                            tok::ObjCKeywordKind ObjCID,
                            IdentifierTable &Table) {