OpenBVE v1.9.2.3

This release adds another significant change, in that it is now possible to uncouple vehicles from the player train. Whilst (probably) not immediately useful, it is another significant step along the path of moving away from the simple linear world model.

Note: Two pre-releases to work out some kinks caused by the new PNG decoder. Hopefully this is now fully functional.

Significant Changes:

• New: Add Slovak language (DuckyProgramator)
• Change: Minor improvement to UK* plugin AI.
• Change: Cache the object optimisation state.
• Fix: Issue with some interlaced .PNG files.
• Fix: Remove memory debug message in 32-bit (KennyHui)
• Fix: Correctly terminate the route preview thread.
• Hacks: Update Tinsford patch.
• Hacks: Add patches for several Polish routes, fixing assorted issues.