Return number of bytes written and read by Write() and Read().
Return number of bytes written and read by Write() and Read().

Because of limitations in PulseAudio's Simple API,
this always returns the length of the buffer on success,
and zero on failure.

For consistency, Drain() and Free() no longer return integers.

Previously all of these returned 0 on success and -1 on failure,
which is redundant with the error value anyway.

Closes #4.

mesilliac/pulse-simple