build: add options for enabling and disabling any libquvi versions

Makes packaging a bit simpler.
build: reimplement the OSS checks using a more declarative approach

The OSS checks were a big mess and quite buggy. This reimplementes them using
a declarative approach and clearly distinguishing between the various OSS
implementations. The code should now almost be auto-documenting.

We currently support the following implementations of OSS:
 * platform-specific (with `sys/soundcard.h`)
 * SunAudio (default on NetBSD and useable on OpenBSD even if we have sndio
   support there).
 * 4Front (default on FreeBSD)

Since now each OSS check also checks for the appropriate soundcard header,
remove the old soundcard check.

Many thanks to @bugmen0t for in depth info about all the BSDs.
Check #380 and #359 for more info on this commit.
build: make deps_neg work with multiple dependencies

Previous code only worked id len(deps_neg) was 1.