Add the include directories found by cmake to the pulseaudio plugin.
This allows for the plugin to compile when the pulseaudio headers were
found in a directory that is not normally in the search path of the
compiler (e.g. /usr/local/include)
The wrapping library uses a global mainloop and context which
allows operations to share the connection. The global mainloop
is created and destroyed based on internal reference counting.
The capture code won't spawn a new thread for each input anymore
but instead just create the recording stream and rely on the
threaded mainloop to execute the read callback when data is available.