[AD] New directsound driver

[Robin Burrows <rburrows@xxxxxxxxxx>]

allegro/src/win/wdsndmix.c

This is an additional directsound driver which uses allegro mixer to fix
a lot of problems (mainly with JGMod). I suggest it is not used as the
default, but should be selectable via the setup prog or other means.

Gotchas:
It is written by me, so be warned there may be bugs...
At the moment I think it will only work as a replacement for wdsound.c
as I don't understand the _get_digi_driver_list hook. This may have to
be fiddled with. The names are different to wdsound.c (drivers are
prefixed with 'Allegro ') but the IDs are identical.
I am using timeSetEvent to add the callback as install_int didn't work,
if there is a better way, please change it.

Attachment: wdsndmix.c
Description: application/unknown-content-type-c_auto_file