Add CMake build system

This should hopefully work torwards compatibility with more systems.
I've tried to make this as general as possible but some small assumptions
about the compiler are made. I've also tried to recreate the build process
as closely as possible, but I had to change some things slightly to work
with CMake (version strings, mainly).

For now, it doesn't allow in-source builds, as that could overwrite the
Makefile.

This adds:

- Support for more build systems
- Automatic dependency generation
- Performance gains (especially when using i.e. Ninja)

Defaults to Release build.

.gitignore

@@ -6,6 +6,9 @@ rgbshim.sh
 *.o
 *.exe
 .checkpatch-camelcase.*
+CMakeCache.txt
+CMakeFiles
+cmake_install.cmake
 
 test/pokecrystal
 test/pokered