ZVISION: Implement several advanced engine features and ScummVM dialogs

The functionality to return to launcher, list saves, delete saves, load
games from the launcher and load and save games during runtime has been
implemented. Also, ScummVM save/load dialogs have been implemented.
Saved games now have three numbers in their file extension, bumping the
possible save game slots up to 999
ZVISION: Add some spacing
ZVISION: Remove unused code
SCUMM: Maniac V0: Add support for D64 Demo Disk, Cleanup duplicate 'Talk' array
ZVISION: Implement more advanced engine features

Save game thumbnails and save game creation date have now been
implemented
SCUMM V1-V2: Fix actor walk behavior (transitions between walk boxes, and changing destination issue)
SCUMM: Maniac V0 Demo: Allow F7 to restart, Add handler for opcode 0x6e (o_screenPrepare)
Merge pull request #546 from segrax/V0_Demo

SCUMM: Maniac V0: Add support for D64 Demo Disk, Cleanup duplicate 'Talk...
Merge pull request #542 from segrax/V1-V2_WalkAnimFix

SCUMM V1-V2: Fix actor walk behavior (transitions between walk boxes, and changing destination issue)
SCUMM: Correct variable type in Actor_v0::adjustPosInBorderWalkbox, since variable can have negative value.
CONFIGURE: Add likely fix for AmigaOS4 linker relocation build failure.