PulseAudio 4.0

Based on https://github.com/mxcl/homebrew/pull/18838

PulseAudio 4.0 has been released.  4.0 contains fixes for two bugs causing problems in the last pull request, https://bugs.freedesktop.org/show_bug.cgi?id=62988 and https://bugs.freedesktop.org/show_bug.cgi?id=63014 .