gst_ks_device_provider_probe() is a no-braier, just runs ks_enumerate_devices()
and reports the results.
Monitoring is a bit more tricky. We have to create a dummy message-processing
window and register device change notifications for it.
As kernel streaming can (and should) be used for audio capture and audio
playback, this change also has certain placeholders for such.
https://bugzilla.gnome.org/show_bug.cgi?id=747757
Most important part here is special-casing "device busy" so the application
is able to provide better feedback when another application is using the
device.
Original commit message from CVS:
* configure.ac:
* sys/Makefile.am:
* sys/winks/Makefile.am:
* sys/winks/gstksclock.c:
* sys/winks/gstksclock.h:
* sys/winks/gstksvideodevice.c:
* sys/winks/gstksvideodevice.h:
* sys/winks/gstksvideosrc.c:
* sys/winks/gstksvideosrc.h:
* sys/winks/kshelpers.c:
* sys/winks/kshelpers.h:
* sys/winks/ksvideohelpers.c:
* sys/winks/ksvideohelpers.h:
New plugin for low-latency video capture on Windows (#519935).
Uses Kernel Streaming, the lowest level API for doing video capture
on Windows (more or less just raw ioctls).
