- DEBUGMODE
- MOBJCONSISTANCY
- PACKETDROP
- ZDEBUG
- PROFILEMODE (likely moot, dunno how profiling with cmake works
though)

Adds SRB2_CONFIG_ERRORMODE to replace ERRORMODE too.

Simplifies build setup for cmake.

Improves ccache support for Xcode

Overhaul cmake build

See merge request STJr/SRB2!1832

(cherry picked from commit 4337205f)

# Conflicts:
#	src/sdl/CMakeLists.txt

- target_sources from correct directory
- enable_language must be used in add_executable directory

This establishes (near) parity of source code file lists
between the Makefile and CMakeLists.txt

To make that change I messed around CMakeLists.txt a bit.
It now uses target_sources and target_compile_definitions.
I also removed some MSVC stuff since we don't actually
care about MSVC--it made things easier.

CMake minimum version 3.0 -> 3.13 for target_sources.

Some key points for programmers:
- Source code files are mostly listed in a 'Sourcefile'.
  So you no longer directly edit the object list. There
  can be multiple Sourcefiles and they can even live in
  subdirectories--the directory name will be prepended to
  every filename in the list. Of course, the Makefile
  still needs to be edited to read from each Sourcefile.
- Different rules are no longer required for source code
  files that live in subdirectories (such as sdl/ or
  hardware/). Subdirectories Just Work so go ham!

In addition to those points, another important change is
that the bin directory is no longer divided into platform
subdirectories (Linux64, Mingw, etc). Executables now go
directly into bin. If you use DEBUGMODE or target 64-bit,
then subdirectories for 'debug' and '64' will be made
though.

Oh by the way, I don't think make clean actually removed
files before on Windows. It should now. I also fixed as
many little inconsistencies like that as I noticed.

And now just an overview of the technical aspects that
shouldn't affect anyone who doesn't REALLY care about the
Makefile...

objs and dep directories have been moved to a make
directory. Makefile.cfg and its variants have been moved
out of their various subdirectories to src/Makefile.d
make distclean removes the bin and make directories
entirely, but make clean and cleandep still only affect
the current build target.

When I say automation, I mean that a lot of copy pasting
in the Makefile has been reduced.

CMake support. Srb2win.rc still needs touchy, whatever.

Also updated CMakeLists.txt, appveyor.yml and this one Xcode project file as usual

This reverts commit d03c5393.

Don't worry, I remembered to update MODVERSION as well this time :)