Implement recursive sorting of a single playlist node from popup menu,
in either ascending or descending order. Node is sorted by values in
column which was right clicked to bring up the popup menu.

They don't have AM_DEFAULT_VERBOSITY.

This enables drag items from service discovery, I don't see why user
shouldn't be allowed to drag his/her favorite shoutcast/other item to
medialibrary or playlist from service-discovery lists.

Add new function which simplifies moving more then one item at a time and
reduces complexity and increases performance of such action.
Also refactor a bit old playlist_TreeMove.
Use new function in Qt4 playlist model.

This enables Linux kernel-style silent build output.

If you want a more verbose output use 'make V=1' or './configure --disable-silent-rules'

If you want even less verbosity for custom command, there is $(AM_V_GEN) that you can add in front of your custom command.

And remove a few unnecessary casts.

Fix provided by NightStrike from mingw-w64 project

This will let us have a few extras widgets in the main dialog

( PLModel::childrenCount() > 0 ) is not equivalent to (
playlist_item_t*->i_children > -1 ). This patch swaps former for latter
which is a correct strict check wether an item is node.
Signed-off-by: Ilkka Ollakka <ileoo@videolan.org>