fix gcc warning (-Wdeprecated-declarations)
fix gcc warning (-Wunused-parameter)
highlight drag&drop target
partially rewrite queue manager

changes:
* change appearance: use standard window type, hide progressbar instead of
  writing "unused" on it
* add more job details in the queue window
* add ability to delete the last queue
* fix bug: source was not written for virtual copy & virtual move jobs
use tristate checkboxes instead of comboboxes for permissions in advanvced filter
speed up viewing contents of folders containing many files
make mouse XButton1/XButton2 move backward/forward in history