Attention packagers: New optional dependency on libpulse

As you may have noticed, Wine recently integrated the PulseAudio audio
backend. This obviously introduces a dependency on libpulse, in 32-
and/or 64-bit forms depending on what you're building. Building
winepulse will be enabled at configure-time if libpulse is present,
otherwise winepulse will not be built. If PulseAudio is not running,
or libpulse is not installed, Wine will fall back on another driver.

Thanks,
Andrew