Set registry ISO10646 at run time

We don't know at compile time whether the X server even supports
Unicode. So take the configured map font, change the registry to
ISO10646 and try the resulting font string. Keep the configured
font if that doesn't work.

include/winX.h

@@ -64,6 +64,10 @@ struct text_map_info_t {
         square_height, /*   we can calculate the correct */
         square_ascent, /*   placement of changes.        */
         square_lbearing;
+
+#ifdef ENHANCED_SYMBOLS
+    XFontStruct *font;
+#endif
 };
 
 struct tile_glyph_info_t {