[CMake] CMake and user friendliness

[Drew DeVault]

I've been using cmake for a few months now, and I wanted to provide some
feedback compared to autotools.

First of all, from a developer perspective, I love cmake. It's much,
much better than autohell and I really appreciate it.

However, from a user perspective (i.e. someone compiling and installing
software), autotools is much, much better. Compare this:

./configure --enable-sdl --disable-readline

To this:

cmake -DENABLE_SDL=No -DENABLE_READLINE=No .

And figuring out how the configuration works is a pain, too. Compare this:

$ ./configure --help
...
Optional Features:
  --enable-sdl		enables the SDL frontend
  --disable-readline	disables the readline frontend
...

to this:

$ cmake -LH
// Enables the SDL frontend
enable-sdl:BOOL=YES