- fix compatibility with newer versions of FreeBSD

- fix compatibility with newer versions of FreeBSD
- fix all warnings during compilation
- fix obvious bugs
- add support for more cards

Now supported:
 - M-Audio Delta Dio 2496
 - M-Audio Audiophile 2496
 - Terratec DMX 6fire

Known bugs (detected by Nokolas and Stefan):
 - $ kldunload snd_ak452x.ko
   Warning: memory type ak452x leaked memory on destroy (1 allocations,
   64 bytes leaked).
 - No sound in KDE: Everything works fine at the console but when I load KDE
   (3.5.3) the sound stutters and plays at less then 1/2 speed.
 - 'mixer: WRITE_MIXER: Device not configured' The message repeats x
   times at system startup, x = whatever hw.snd.maxautovchans is set to.
   (this is because only vol, pcm and line are supported, but the driver
   shows more than those mixer devices and setting those additional mixers
   results in this error message)
 - vchans don't work
 - 24 bit playback not supported (only 16/32 bit)
 - after kld(un)loading some times, the card fails to be probed until reboot

Datasheets are available from:
	http://www.nbritton.org/uploads/envy24/
	http://www.asahi-kasei.co.jp/akm/en/product/ak4528/ak4528_f01e.pdf
	http://www.asahi-kasei.co.jp/akm/en/product/ak4528/ekd4528-01.pdf
	http://www.asahi-kasei.co.jp/akm/en/product/ak4524/ak4524_f03e.pdf
	http://www.asahi-kasei.co.jp/akm/en/product/ak4524/ekd4524.pdf
	http://www.wolfson.co.uk/uploads/documents/en/WM8728.pdf
	http://www.richtech.co.kr/down/richtek/RT9131.pdf
	http://xkodi.svobodno.com/xkodi/space71.html
	http://people.freebsd.org/~lofi/envy24.pdf
	http://people.freebsd.org/~lofi/4524.pdf

Submitted by:	Konstantin Dimitrov <kosio.dimitrov@gmail.com>
Tested by:	Nikolas Britton <nikolas.britton@gmail.com>
		Stefan Ehmann <shoesoft@gmx.net>