* vlc_symbols.h, vlc_playlist.h, view.c : add a function to remove a parent from...

* vlc_symbols.h, vlc_playlist.h, view.c : add a function to remove a parent from the parent list of an item (if anybody wants to make that another way...)
* playlist.m: implements full drag and drop of playlist items. Drop of multiple items and of items and nodes at the same time should be supported. You cannot mode service discovery items. This is a choice and can be changed if wanted.
* Hopes that compiles on current trunk (cannot check since latest comits on net functions broke the built of a half the modules and core of the OSX port...)