Configurations: all 64 game configuration are now available by default.
Game Configurations window: game configurations can now be disabled. This setting is mostly cosmetic. When a game configuration is disabled, it won't be shown in "game configuration" dropdowns in New\Open Map Options and Map Options windows. If a map's .dbs file specifies a disabled configuration, it will be picked as a map configuration anyway.
Linedefs mode: vertex insert preview logic used Highlight range instead of Stitch range (which is used when draw mode engages).
Visual mode: double-sided middle textures were not selected when using "Select" action with "with same texture" modifier.
Textures: some optimizations in patch blending code.
ZDoom ACS script configuration: added definitions for StrLeft, StrMid and StrRight functions.
Texture scale controls now have "Link" button.
Thing, Sector (UDMF) and Linedef edit forms now work in realtime mode.
Some more fixes in Edit form realtime update stuff.
Removed some unused variables and functions.
