(panel_get_title_without_hotkey): return pointer to static buffer

...to avoid extra memory allocation.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(do_enter): make inline and return gboolean instead of int.

(do_enter_on_file_entry_t): rename back to do_enter_on_file_entry and
return gboolean instead of int.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>