CGE2: Heavily rework memory management of Sprites.

Hopefully it will solve a bunch of memory leak problems.
Now Spare is a central container, which stores pointers to every Sprite currently used by the engine.
Because of that, there's no more need for Queue's clear().
In case of snKill(), it's just a safeguard, since it's only used by the engine to "kill" the speech bubbles, but we will check Spare anyway, so it's the safest this way.
CGE2: Silence warning.
CGE2: Partially working save/load system.

There's a mayor bug which blocks the toolbar from interaction after loading. To be investigated during the upcoming days.
CGE2: Remove unnecessary parameter from Spare::sync().
CGE2: Rename saveHeroPos() to storeHeroPos().
CGE2: Rename and heavily rework Bitmap::forceExt().

Since the extension is always ".VBM" in case of Bitmaps, there's no need to pass it as an argument.
CGE2: Replace addExt() wit setExtension().
CGE2: Fix broken compilation by previous commit.
CGE2: Fully implement the save/load system.

Now the toolbar is working too after loading.
CGE2: Remove unnecessary warning and debug info from showTitle().
CGE2: Implement loading from the Launcher.
PRINCE: Background animations update. O_PUTBACKANIM(), O_REMBACKANIM(), O_ANIMUPDATEON(), O_ANIMUPDATEOFF()
PRINCE: O_GETOBJDATA(), O_SETOBJDATA()
SCUMM: Add support for CD audio tracks in the Steam versions of Loom

Many Thanks to Ben Castricum for the original patch
OPENGLSDL: Don't ignore events after user-initiated resizes.
CGE2: Add extra clipping to Bitmap::hide
Merge pull request #470 from bluegr/Lucasarts_Steam

SCUMM: Add support for Steam versions of Indy 3, Indy 4, Loom and Dig
SCUMM: Remove empty line before license header.
SCUMM: Use spaces instead of tabs in comments.
SCUMM: Remove unused variable.