sound: Adjust mmap example to use kqueue

[meka_tilda.center]

Summary

With D57362 mmap is much easier and efficient to handle using kqueue, so mmap.c is change to reflect that.

[meka_tilda.center]

In previous patch I acidently included kernel and map page patch, so this is a clean one.

[christos]

share/examples/sound/mmap.c

40–41

Are all these needed here?

92

Can't we just re-use ev?

175

Should these be errx()s or warnx()s? In other words, are these fatal errors?

182–183

[meka_tilda.center]

Address the comments.

[meka_tilda.center]

share/examples/sound/mmap.c

175

If ptr is out of bounds, it's a bug and we should bail out. Same goes for frame_size, which is sample_size * channels. If ptr is not multiple of frame_size, that means we're somewhere in the middle of the frame or even worse, middle of a sample. That's also a bug and we should bail out.

[meka_tilda.center]

Forgot one of the comments.