Add an addition operator to TableGen

This adds an !add(a, b) operator to tablegen; this will be used
to cleanup the PPC register definitions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173445 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/TableGen/TGLexer.h b/lib/TableGen/TGLexer.h
index e2e116b..a0818f9 100644
--- a/lib/TableGen/TGLexer.h
+++ b/lib/TableGen/TGLexer.h
@@ -46,7 +46,7 @@
     MultiClass, String,
     
     // !keywords.
-    XConcat, XSRA, XSRL, XSHL, XStrConcat, XCast, XSubst,
+    XConcat, XADD, XSRA, XSRL, XSHL, XStrConcat, XCast, XSubst,
     XForEach, XHead, XTail, XEmpty, XIf, XEq,
 
     // Integer value.