v17.7-dev19 - "huge" update - fixes ground-water textures and transparent NPCs

All thanks to the work of @SaiyansKing, who implemented a bunch of stuff:

• a4c8e16
  • Fix wrong materials after level change (e.g. water textures on walls and ground)
  • improved GPU Memory usage
• 5ab1557
  • fix disappearing water in some cases (e.g. Jharkendar ocean suddenly missing)
• 3895d53
  • optimized rendering of skeletal vobs (e.g. NPCs)
• fcb7b71
  • properly render "ghosts" with transparency
• eb3ad3a
  • fix disappearing chapter screen
  • fix broken render states in some circumstances
  • added "support" for G1 Sequel (currently no release)