baseparse: remove pending_segment as it was being misused
baseparse: remove pending_segment as it was being misused

It wasn't required, instead baseparse was using it to check the media
caps to identify if it was handling audio or video.

The pending_segment was removed and a checked_media boolean
replaced it for a more accurate naming.

https://bugzilla.gnome.org/show_bug.cgi?id=721350

justinjoy/gstreamer,justinjoy/gstreamer,justinjoy/gstreamer,justinjoy/gstreamer,justinjoy/gstreamer