keymaps: Use multiple key maps, each within the limit of what Xorg can accept.

Key maps are switched on key press whenever needed.

src/layout.h

@@ -39,7 +39,6 @@ struct transformation squeek_layout_calculate_transformation(
         double allocation_width, double allocation_size);
 
 struct squeek_layout *squeek_load_layout(const char *name, uint32_t type);
-const char *squeek_layout_get_keymap(const struct squeek_layout*);
 enum squeek_arrangement_kind squeek_layout_get_kind(const struct squeek_layout *);
 void squeek_layout_free(struct squeek_layout*);