avformat/network: add union for avoiding strict aliassing violations with sockaddr*

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/rtpproto: fix strict aliasing violations with sockaddr

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
RELEASE: update to 2.4.git

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: James Almer <jamrial@gmail.com>