removing sndio support from openal-soft

[Evgeni Golov <evgeni@debian.org>]

Hi Andres, hi rest of pkg-games,

ron and waldi asked to remove libsndio (libroar) from openal-soft.

The rationale behind is as follows:
- libopenal1 recommends libroar-compat2 depends libroar2 depends
libdnet, libcelt0-0
- libcelt is planed to be removed from the archive but libroar did not
lose that dep yet (#674649)
- libdnet suggest (but actually should recommend) dnet-common, but with
that, it will land in the default install and promt the users stupid
questions (see also #675014)

I disabled sndio support for openal-soft in 01a7170 and would like to
upload it soon -- any objections from you here, at least you enabled it
some reason?

Regards
Evgeni