abuf_flush() must be called only from the ``xxx_in()'' routines (ie

abuf_flush() must be called only from the ``xxx_in()'' routines (ie
triggered by POLLIN condition).

mix_pushzero() is not called from the ``xxx_in()'' chain, but calls
abuf_flush() resulting in bad initialization of the mixer, which
will lead to a deadlock at some point.

ok jakemsr