Fix for a regression from commit 8f1384c9. That commit moved the debug
category definition, as static, into a gstvideocropelement.c, but that
category was used as default, in gstvideocrop.c, so it was never used
at logging, so the debug selector never showed the logs for
videocrop.
This patch move back the category definition into gstvideocrop.c and
leaving the function videocrop_element_init() as a noop.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/1049>
When an caps-event is received, we must immediately change the crop
to videocrop correctly changed caps-event dimension, otherwise the
videocrop will first use the previous value of the crop that when
resizing video to a smaller resolution may cause an error.
https://bugzilla.gnome.org/show_bug.cgi?id=740671
