Some little fixes for bapt’s patch, use predict_text_width, support UTF8, pre-render workspace names

include/data.h

@@ -165,9 +165,12 @@ struct Workspace {
         /** Number of this workspace, starting from 0 */
         int num;
 
-        /** Name of the workspave */
+        /** Name of the workspace (in UCS-2) */
         char *name;
 
+        /** Length of the workspace’s name (in glyphs) */
+        int name_len;
+
         /** x, y, width, height */
         Rect rect;