We've replaced/changed out all vanilla songs, so we no longer need it.

Disabling DEVELOP can be another branch; this means this can get in master quicker

UNFINISHED, still need to add in legitimate hashes for non-CMake builds when we've finalized the content.

Splitscreen in Battle is left

Core and SDL2 are two separate targets now. Core is a static library
that is linked into SRB2SDL2. The sources for both are separated.
When using an IDE like Visual Studio or Xcode, the source code
organized into groups that explain what that group of sources does.

In the future, "Main" could be split into a few more groups based on
file prefixes, but I think the way it is set up works for now.

Makefile targets are not affected by source_groups and typing `make`
will automatically compile both the "Core" library and SRB2SDL2
itself.

silently fixing a bad malloc here too shhhhhhhhh

Generates zips only at the moment