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"
SCI: Add missing USE_MAD check for commit 6a519f7f

This fixes compilation for platforms where libmad isn't present
FULLPIPE: Implement sceneHandler29_shootersEscape()
FULLPIPE: Implement sceneHandler29_sub07()
FULLPIPE: Implement sceneHandler29_sub15()
TSAGE: Fix incorrect cursor when changing R2RW desert areas
ALL: Resolve multiple clang warnings
FULLPIPE: Implement sceneHandler29_sub16()
Merge pull request #456 from fingolfin/clang-fixes

ALL: Resolve multiple clang warnings