instead of three submodule and no main module!

A new playlist item flag stops playlist after the item gets subitems.
The flag is set only upon user request to play an item from Qt views and only
if he does so in playlist "tree mode" not "one level".
Behavior on items played when playlist advances is unaffected.
This allows for comfortable "browsing" of playlist in tree mode, in particular
when using the Qt interface's icon view.

- When input changes, update visible item after currentItem has been set.
- Check if item is current when adding it.

value to something more sensible if desired.

This is the patch as supplied, which needs work and as of yet doesn't
compile on non-unix. Fixes pending. -- jpd

This reverts commit 714ef56a.

By popular demand.

If we receive a currentChanged, and currentView ain't set, we might crash in
handleExpansion

Crashes have happened at
StandardPLPanel::handleExpansion (this=<value optimized out>, index=@0x406b56a0) at
components/playlist/standardpanel.cpp

Spotted by jpeg.