Search callbacks should return mc_search_cbret_t not int.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
mcviewer: adjust start search position.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
mcviewer: apply status message for search process.

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