Screenshot textures would be renamed to "<mapname>_screenshot.png", making it explicit that this texture is a screenshot texture.
This fixes a potential bug wherein the screenshot texture could unintentionally override other textures if the map's name matches the texture name. e.g. moon.png - this would now be renamed to moon_screenshot.png.
Three new map meta fields are now available to map makers:
- `phys_speed`: Speed multiplier
- `phys_jump`: Jump multiplier
- `phys_gravity`: Gravity multiplier