The plugin often uses "pa_" for its internal structures
and functions, which is misleading because this prefix is
also used by PulseAudio itself. Thus, reading the code can
be confusing.
Rename everything to "agl_".
Change-Id: Iadd03daf528ec0cbed1cb526aeb3bada757a211f Signed-off-by: Manuel Bachmann <manuel.bachmann@iot.bzh>