document !strconcat

llvm-svn: 30032

llvm/docs/TableGenFundamentals.html

@@ -322,6 +322,8 @@ supported include:</p>
 <li><tt>(DEF a, b)</tt> - a dag value.  The first element is required to be a
 record definition, the remaining elements in the list may be arbitrary other
 values, including nested `<tt>dag</tt>' values.</li>
+<li><tt>!strconcat(a, b)</tt> - A string value that is the result of
+ concatenating the 'a' and 'b' strings.</li>
 </ul>
 
 <p>Note that all of the values have rules specifying how they convert to values