Add support for max-framerate in the video helpers and update the video
caps document.

They got somehow commited in 7012e880

gst_basertppayload -> gst_base_rtp_payload
Add pts/dts support in the depayloader
Remove old timestamp code
Add a default getcaps function so subclasses can chain up to it instead of
relying on the return value of the getcaps function.

Don't assume the format is a string because now it is a list of string in the
template.
Chain up to the parent class implementation of get_caps.

Otherwise the resulting caps may not be fixed.

Those are valid, and the EOS skeleton packet is actually empty.

https://bugzilla.gnome.org/show_bug.cgi?id=663766

Fixes #663689

Conflicts:
	common
	ext/pango/gsttextoverlay.c
	gst-libs/gst/video/video.c

It was only used by playbin, which is gone now

Rename object to avoid conflicts with an object of the same name in core.

https://bugzilla.gnome.org/show_bug.cgi?id=662952

This prevents playback wegding when text buffers are
left to pile up.

https://bugzilla.gnome.org/show_bug.cgi?id=662829