pulse: rework buffering and fix overflow

Principal aout modules already handle a big buffer (more than 5sec), only pulse is not.

Therefore, overflow could happen on Linux, when the user was adding delay via the sync dialog.

We could think about few improvements:

• Handle the big buffer in the core (instead of the module) in order to react immediately to filters. We need to add a data callback in aout modules to make it work (more for 5.0)
• Limit the audio buffer size in all modules to a given amount. Or we could limit the input pts_delay and audio desync that has a direct link to the audio buffer size.