libavformat: Fix standalone compilation of the webm muxer

The missing object file was added to the matroska muxer already, but
not to the webm muxer.

Signed-off-by: Martin Storsjö <martin@martin.st>
rtpdec: Fix the alphabetical ordering in registering depacketizers

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge commit '2681924b0f3f35840dd9d9825df9f9239c448b22'

* commit '2681924b0f3f35840dd9d9825df9f9239c448b22':
  libavformat: Fix standalone compilation of the webm muxer

Conflicts:
	libavformat/Makefile

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  rtpdec: Fix the alphabetical ordering in registering depacketizers

Merged-by: Michael Niedermayer <michaelni@gmx.at>
flvdec: Fix mistakenly discarding metadata at dts==0

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>