Alternative sprites for RTL language suppot #405
Description
Grfcodec now (OpenTTD/grfcodec#46) and OpenTTD will presumably soon (OpenTTD/OpenTTD#14188) support alternative sprites for RTL languages, for example a left-pointing fast-forward or play button make more sense in RTL languages. This is encoded in bit 4 in the sprite info byte.
NML support would be appreciated!