API finalizing

[calvin]

The player library API is not really finished, and in CPlayer there is f.ex not a clear distinction between the internal stuff and the "public" methods intended for library clients.

CPlayer should have a clear, public API with all the dirty stuff hidden in a CPlayerInternal similar to what CMachine has. It should hide the mixer and sequencer members, and provide methods to manipulate everything in a thread safe manner.

How that things are starting to work quite well, this is becoming rather critical, so clients (i.e UI) can get a stable API to work against.