wlmaker

toolkit: Eliminates wlmtk_element_pointer_enter and wlmtk_element_pointer_leave, now handled by signals.

toolkit: Migrates wlmtk_menu_item_t off the enter/leave virtual methods to the signals.

toolkit: Migrates wlmtk_button_t off the enter/leave virtual methods to the signals.

toolkits: Adds pointer_enter and pointer_leave events to wlmtk_element_t.

toolkit: Replaces memcpy by direct struct assignment.