Fix sync notifications
Fix sync notifications

Correctly handles sync locking, quits iPod app at sync start, and has
saner error handling.

Note: the repeated sync retries are required. The iPod app will fade-out
and take over 4 seconds if sync starts while music is playing. The
current timeout is 50*200ms = 10 seconds, which should be reasonable.

hyperair/libgpod,hyperair/libgpod,hyperair/libgpod,neuschaefer/libgpod,neuschaefer/libgpod,hyperair/libgpod,neuschaefer/libgpod,neuschaefer/libgpod,hyperair/libgpod,neuschaefer/libgpod