access: srt: introduce srt input module

Secure Reliable Transport (SRT) is a proprietary transport technology
that optimizes streaming performance across unpredictable networks.
This patch is an imlementation of input module which works as a SRT
client based on SRT Library[0].

[0] https://github.com/Haivision/srt/releases



Signed-off-by: Justin Kim <justin.kim@collabora.com>
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>