Make xml consumer respect video_off and audio_off.
Document sepia filter.
GstSHM: Initial import.

What we are building is a pair of producer and consumer that link
various melt processes via shm using the same control semantics
as the shmsink / shmsrc GStreamer elements.

The on memory format is not compatible with GStreamer but elements
to mux and demux it will come soon.

See README for more details.
WIP: adds 4 buffers so GST is happy, verbose logging.

really need to cleanup this
consumer: make debugging log conditional.
producer: do not skip first frame.
producer: got rid of cache, some cleanup.

I know this will bite me later ...
producer: make debugging optional
wip
serialize access to sp_*

it was the only thing that the docs asked...
cleanup debugging
adds headroom to memsize calculation.

Sometimes we get a frame with 1600 audio samples, others 1604. If
at the start we get the shorter one things get interesting.
whitespaces
gstshm producer: adds hi/lo watermark method to control internal
buffering.
reduce the scope of locks and conditions.
try to operate in push mode when using gstshm as both the consumer and
producer.
updated license and authors