Core code has too many #define dependencies on interface-specific
defines. This means that it's currently not possible to safely
separate the core and interface code into different contexts. The
core code should be refactored to accomadate for this because we
should not have any interface-specific code in core in the first
place.
This reverts the static library SRB2Core from a7135094 and instead
adds the core sources to the SRB2SDL2 target directly.
So frustrating...
It is really messy at the moment. There is no support for copying the
necessary frameworks and dylibs out to the bundle for distribution, and
it is a frankenstein of manual find_library and find_package which can
sometimes pick up Homebrew dylibs.
