Add meson_option to build without PulseAudio Widget

[ErikReider]

Fixes: #271

meson build -Dpulse-audio=false configures it to build without PulseAudio

[ErikReider]

@freijon If this works as expected on your end, I'll merge it :)

[freijon]

Hello @ErikReider

Thanks! I created a test package and the new option works like a charm.
The only thing I notice is that the man-pages still have the the pulse-stuff in them even if built without pulse. I patched that out as well in our package. I'd consider this a bonus goal though ;)

[ErikReider]

I'll check if there's a way of patching out sections through meson

[ErikReider]

The only thing I notice is that the man-pages still have the the pulse-stuff in them even if built without pulse

Added a "hacky" way of doing this. It works like a charm though :)