FULLPIPE: Implement sceneHandler29_clickPorter()
COMMON: Reduce the warnings related to backwards seeking in ZIP files

The warnings are now changed to debug statements, are only shown once
per session (instead of once per stream) and are only enabled for debug
builds.
SCI: Initial implementation of the fanmade sciAudio library

This is used in the fanmade games "LockerGnome Quest Redux" and
"Betrayed Alliance"