Revert "Audio: Make cheap OpenAL pitch shifting a config option"

Making this an option makes no sense. It ought to
be the default behavior, as RMXP pitch shifts PCM
based audio files the exact same way.

This reverts commit ac35d4214e380afc3a09d03b64c2ae714f4fbe9b.
Audio: Remove all traces of rubberband

We will not be using librubberband for in place
pitch shifting. RMXP "shifts" PCM based audio
by just playing it back slower/faster, which
OpenAL takes care of for us. A native midi backend
will be able to effortlessly pitch shift by
multiplying note pitches, should we ever get one.

I have been chasing this ghost for way too long.
Bitmap: Fix renaming issue in RGSS2 code
Audio: Implement RGSS2 ogg looping

With this we now link to libvorbis/ogg directly.
When this is enabled, one can theoretically also
build SDL_sound without ogg support, although I
doubt it makes much of a difference.

Adittionally, count frames instead of samples
for playback offset calculation.
mkxp.pro: Don't xxd unneeded resources
Audio: MeWatch: Don't resume stopped BGM
Sanitize #include statements

The general rule I'm aiming for is to <> include
system wide / installed paths / generally everything
that's outside the git managed source tree (this means
mruby paths too!), and "" include everything else,
ie. local mkxp headers.

The only current exception are the mri headers, which
all have './' at their front as to not clash with
system wide ruby headers. I'm leaving them be for now
until I can come up with a better general solution.