Escape tabs in lua-make-lua-string

Doing so prevents comint from intercepting the tabs and passing them to
the underlying shell process, which inserts shell tab completion text
into the code string, mangling it so that it can't run.

lua-mode.el

@@ -1708,10 +1708,14 @@ This function just searches for a `end' at the beginning of a line."
     (with-temp-buffer
       (insert str)
       (goto-char (point-min))
-      (while (re-search-forward "[\"'\\\n]" nil t)
-        (if (string= (match-string 0) "\n")
-            (replace-match "\\\\n")
-          (replace-match "\\\\\\&" t)))
+      (while (re-search-forward "[\"'\\\t\\\n]" nil t)
+        (cond
+	 ((string= (match-string 0) "\n")
+	  (replace-match "\\\\n"))
+	 ((string= (match-string 0) "\t")
+	  (replace-match "\\\\t"))
+	 (t
+          (replace-match "\\\\\\&" t))))
       (concat "'" (buffer-string) "'"))))
 
 ;;;###autoload