[OpenTTD] Improved 32 bpp support

[Michi_cc]

With r23002 the 32 bpp support in OpenTTD was improved.

It is now possible for graphics base sets and NewGRFs to give OpenTTD a hint that they prefer a 32 bpp blitter. OpenTTD will try to honour that hint and switch blitters automatically, but will ignore it if necessary. Only 8 bpp sprites are guaranteed to work with any blitter, so 8 bpp fallback sprites are still necessary even with a 32 bpp hint.

For NewGRFs, this hint is given via Action 14. For graphics base sets, the obg file format was extended.

-- Michael Lutz

[Lord Aro]

excellent! thanks! this should be very helpful
now, to learn how to make newgrfs