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

46

Are all these needed here?

100

Can't we just re-use ev?

183

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

190–191