Make ui.c:swap_view_roles() non-static
Fix segfault on running vifm with 1 arg

Restored cursor should be in the right pane.

Thanks to Svyatoslav Mishyn, a.k.a. juef.
Remove local options loading from swap_view_roles

It's not what it's meant to do.

Also update comments for change_window() and swap_view_roles().
Make local pointer in swap_view_roles() const

Just in case.
Extract vifm.c:need_to_switch_active_pane()

Whether active view should be switched.  Returns non-zero if so,
otherwise zero is returned.
Merge branch 'fix-startup-segfault'

Fix segmentation fault on running vifm with single argument if restored
cursor is in the right pane.

Thanks to Svyatoslav Mishyn, a.k.a. juef.