Do not wrap filemode column in diffstat table

The diffstat looks rather ugly when the filemode is wrapped to one
char per line, so lets force it to not wrap.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.css

@@ -266,6 +266,10 @@ table.diffstat td {
 	border: none;
 }
 
+table.diffstat td.mode {
+	white-space: nowrap;
+}
+
 table.diffstat td span.modechange {
 	padding-left: 1em;
 	color: red;