* ALL: playlist API changes

What may be broken (untested):
------------------------------
   - Theora and Speex decoders
   - some interfaces
   - VCDX and CDDAX access

The problems shouldn't hopefully excess compilation glitches.
(removal of AddExt, of psz_author, and prototype of Add)

Additionnaly, interfaces that do not support item-change will have
update problems.

* Updated modules list