colourTransform is a struct with only one member, a Uint32. The issue
with `Uint32`s is that it requires a bunch of bit shifting logic to edit
the colors. The issue with bit shifting logic is that people have a
tendency to hardcode the shift amounts instead of using the shift amount
variables of the SDL_PixelFormat, which makes it annoying to change the
color masks of surfaces.
This commit fixes both issues by unhardcoding the bit shift amounts in
DrawPixel and ReadPixel, and by axing the `Uint32`s in favor of using
SDL_Color.
According to the SDL_PixelFormat documentation (
https://wiki.libsdl.org/SDL2/SDL_PixelFormat ), the logic to read and
draw to pixels from colors below 32-bit was just wrong. Specifically,
for 8-bit, there's a color palette used instead of some intrinsic color
information stored in the pixel itself. But we shouldn't need that logic
anyways because we don't use colors below 32-bit. So I axed that too.
If it's at all possible to use `const std::string&` when passing
`std::string`s around, then we use it. This is to limit the amount of
memory usage as a result of the frequent use of `std::string`s, so the
game no longer unnecessarily copies strings when it doesn't need to.
This is a pretty hefty commit! But essentially, I made a new editorclass
object, and moved all functions and variables that only get used in the
in-game level editor to that class. This cleanly demarcates which things
are in the editor and which things are just general custom level stuff.
Then I fixed up all the callers. I also fixed up some NO_CUSTOM_LEVELS
and NO_EDITOR ifdefs, too, in several places.
