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()
CGE2: Add extra clipping to Bitmap::hide
PRINCE: checkSeq() update
ZVISION: Fix puzzle disable condition check
ZVISION: Process events for controls similar to original engine, fix some errors.
PRINCE: installObjects(), setObjId(), O_PUTOBJECT(), O_REMOBJECT(). checkMob(), showObjects(), O_GETRND() update
PRINCE: setVoice() fix
PRINCE: O_COMPAREHI, O_COMPARELO fix, debugger update
PRINCE: Interpreter flags fix.
CGE2: Add workaround for the missing dialogs in room 21 (concert)
PRINCE: LMB, RMB update, texts skipping
PRINCE: Small code clean-up
PRINCE: O_WAITHEROANIM(), O_WAITTEXT()
CGE2: Replace NULL with nullptr everywhere.
CGE2: Hopefully fix memory leak problems regarding _ext.
CGE2: Fix Hero::setCurrent().

This fixes a crash regarding the mechanic on scene 6.