tsdemux: always considers mpeg audio ADTS as mpegversion=2

Submitted by Thibault Saunier @thiblahute

Link to original bug (#728805)

Description

According to tsdemux code, mpeg audio with stream-format=adts will always have mpegversion=2, but aacparse says it can also be mpegversion=4.

For example, on that file: https://dl.dropboxusercontent.com/u/2804070/tron_en_ge_aac_h264.ts tsdemux conciders the stream as being mpegversion=2 but aacparse will change that to being mpegversion=4.

It will not cause much issue in practice but running gst-discoverer on that sample will tell us that the file contains 4 audio tracks 2 with mpegtsversion=2 and 2 other with 4 which is clearly wrong.

I am attaching a patch where we just do not set the version at the demuxer level and let the parser do it, I am not sure it is really correct but as parser are now mandatory it works.

Otherwize we should just parse further in the demuxer to get that info.

Version: 1.x