Diablo and Hellfire have different palettes in `ui_art\black.pcx`.
We now ship our own tiny `black.pcx` that takes priority over the
other ones. This `black.pcx` had the Diablo palette which resulted in an
incorrect palette in the Settings screen.
Split our own `black.pcx` file into `black_diablo.pcx` and
`black_hellfire.pcx` and load the correct one depending on the mode.
* Add MakeRectangle helper to convert from SDL_Rect
* Add Rectangle::inset method for shrinking a rectangle
Turns out some of the other use cases I though this could apply to were actually doing something based on a fixed region
* Simplify initialisation of settings menu rects
The backgrounds can be quite large, for example
the Hellfire title background is a 2.4 MiB PCX file.
Previously, we converted all background to SDL surfaces.
This required extra memory, e.g. the 2.4 MiB Hellfire
title background uses 4.6 MiB as an SDL surface.
Changes the background to render directly from PCX instead
to reduce the allocator pressure.
Gleb Mazovetskiy
Anders Jenbo
Andrew James
obligaron
staphen
qndel
Bubio