MADS: Fix original engine bug with highlighted hotspots between scenes
MADS: Fix class hierarchy for scene group 3
MADS: Hook up scene 321 to scene factory
MADS: Removed redundant method definitions from scene classes
PS2: Add support for building against old SDK if PS2SDK_OLD envvar set.

This will allow compilation using the older SDK until the buildbot
PS2 toolchain SDK can be upgraded and we can confirm the newer SDK
builds are working correctly.
MADS: Further workarounds for player data being accessed during cutscenes
SCI: Disable detection of "SCI Narration Demo" fangame.

This is not supported as it requires network access to use the Google
Translate API, which is not supported by OSystem.
FULLPIPE: Implement ModalSaveGame::setup()
MADS: Implement scene 401
FULLPIPE: Fix ModalSaveGame::setup()
CGE: Replace magic numbers with defines.
MADS: Add an isCursorVisible() method

This will probably be used by the menu class, but it's nice to have nonetheless
SCI: Fix compilation due to wrong preprocessor directive.
PS2: Fix hardcoded library settings to allow building against old SDK.

The autodetection should be fixed or modified to remove these hardcoded
library enables. For now, we add another minor HACK to disable the
troublesome Tremor Ogg Vorbis enable on older SDK, which should fix the
buildbot builds.
MADS: Fix for highlighting and using dynamic hotspots
MADS: Fix for on-screen text no longer being removed
FULLPIPE: Implement ModalSaveGame::processMouse()
FULLPIPE: Implement ModalSaveGame::handleMessage()
FULLPIPE: Implement ModalSaveGame::update()
MADS: Fix a crash when trying to pick up objects that can't be picked