d3dvideosink: First destroy the window, then unregister the class

It's impossible to create another pipeline with d3dvideosink after disposing
the previous one due to some problem in d3dvideosink. The message is: "Unable
to register Direct3D hidden window class".

I've evaluated the problem and it's that UnregisterClass() in working thread is
called before DestroyWindow() and UnregisterClass() does nothing.

https://bugzilla.gnome.org/show_bug.cgi?id=722622
h265parser: Initialize pointer correctly that is never assigned but freed in error cases

Fixes crash on broken streams.

https://bugzilla.gnome.org/show_bug.cgi?id=722669
mpegpsmux: update last_ts to mux correctly

We use last_ts to decide what buffer to mux next so make sure that it
always contains the last known valid timestamp.
mpegtsmux: don't leak pad name when treating events

https://bugzilla.gnome.org/show_bug.cgi?id=722699
h264parser: remove trailling 0x00 bytes as the spec doesn't allow them

The spec states that the last byte of a NAL 'shall not' be 0x00
and it is allowed for byte-stream format to add padding 0x00 for
alignment.

So our parser should strip any trailling 0x00.

https://bugzilla.gnome.org/show_bug.cgi?id=721384
h265parser: remove trailling 0x00 bytes as the spec doesn't allow them

Just like h264, the spec doesn't allow the last bytes of a NAL to be 0x00.
So remove it as it is probably just padding.

This is related to https://bugzilla.gnome.org/show_bug.cgi?id=721384