Ticket #3047: fix mc arguments handling.

Following cases from command line are possible:
  * 'mc' (no arguments):
     active panel uses current directory
     passive panel uses "other_dir" from panels.ini
  * 'mc dir1 dir2' (two arguments):
     active panel uses dir1
     right panel uses dir2
  * 'mc dir1' (single argument):
     active panel uses dir1
     passive panel uses "other_dir" from panels.ini

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3047_panel_dir_fix'

* 3047_panel_dir_fix:
  Ticket #3047: fix mc arguments handling.