rtph264/5depay: ignore marker bit

marker bit is not mandatory, some rtsp library such as live555 set the marker bit at the start and the end of an rtp packet if a virtual method is not implemented in the app

https://live-devel.live555.narkive.com/GhOgFmUz/h-264-rtp-marker-bit

so our depayloaders output buffers like these (rtspsrc ! rtph264depay ! fakesink):

(fakesink0:sink) (25 bytes, dts: none, pts: 0:00:01.450087247

(fakesink0:sink) (21289 bytes, dts: none, pts: 0:00:01.450087247

(fakesink0:sink) (25 bytes, dts: none, pts: 0:00:01.796667985

(fakesink0:sink) (8663 bytes, dts: none, pts: 0:00:01.796667985

buffers such as these ones, different buffers with the same timestamp, are not muxable: qtmux and matroskamux will refuse them for different reasons.

With this patch rtph264depay will output, in the above case, 2 buffers and not 4 and this way the stream can be muxed since the buffers have different pts