patch 8.0.1108: cannot specify mappings for the terminal window

Problem:    Cannot specify mappings for the terminal window.
Solution:   Add the :tmap command and associated code.  (Jacob Askeland,
            closes #2073)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 4a6332b..63aa34c 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3259,11 +3259,18 @@
 		/* Avoid a 1 second delay when the keys start Insert mode. */
 		msg_scroll = FALSE;
 
-		if (!dangerous)
-		    ++ex_normal_busy;
-		exec_normal(TRUE);
-		if (!dangerous)
-		    --ex_normal_busy;
+#ifdef FEAT_TERMINAL
+		if (term_use_loop())
+		    terminal_loop(FALSE);
+		else
+#endif
+		{
+		    if (!dangerous)
+			++ex_normal_busy;
+		    exec_normal(TRUE);
+		    if (!dangerous)
+			--ex_normal_busy;
+		}
 		msg_scroll |= save_msg_scroll;
 	    }
 	}