configure: Fix bz2 configure check for Windows

Due to function decorations on Windows AC_CHECK_LIB can't be used to check for bz2.

https://bugzilla.gnome.org/show_bug.cgi?id=465924
pulsesrc: Implement changing the device while playing

https://bugzilla.gnome.org/show_bug.cgi?id=590768
pulsesrc: De-duplicate code to get the current source output info

https://bugzilla.gnome.org/show_bug.cgi?id=590768
pulsesrc: Add property to find out the device currently in use

https://bugzilla.gnome.org/show_bug.cgi?id=590768
pulsesink: Implement changing the device while playing

https://bugzilla.gnome.org/show_bug.cgi?id=590768
pulsesink: De-duplicate code to get the current sink input info

https://bugzilla.gnome.org/show_bug.cgi?id=590768
pulsesink: Add property to find out the device currently in use

https://bugzilla.gnome.org/show_bug.cgi?id=590768
avimux: unmap the correct buffer

The audio buffer was mapped so unmap it and not the video buffer

https://bugzilla.gnome.org/show_bug.cgi?id=706642
rtpbin: proxy jitterbuffer do-retransmission property
tests: add retransmission example
rtxqueue: add property to configure queue size
multipartdemux: timestamp output buffers based on first input buffer that provided bytes not last

https://bugzilla.gnome.org/show_bug.cgi?id=637754
multipartdemux: remove dynamic sourcpads when going from PAUSED to READY
multipartdemux: propagate discont
videomixer: don't send flush_stop twice.

If we get flush start and a seek we need to only send flush_stop once.

More info at #706441
rtpsession: add some more debug
rtsession: fix locking

We need to take the session lock when getting and manipulating the
source.
configure.ac: Don't set BZ2_LIBS if bz2 is not found
jitterbuffer: only timeout EXPECTED timers on gap

Only timeout the EXPECTED timers when we detect a large seqnum gap.
jitterbuffer: fix types of the retransmission event