srt: move common code to single file

1. code can be shared between access/srt.c and access_output/srt.c
2. created a URL parser for SRT parameters stored in URL

Signed-off-by: Thomas Guillem <thomas@gllm.fr>
(cherry picked from commit 15dea8ec) (edited)
edited:
* access out was missing dummy.cpp on 3.0

Signed-off-by: Steve Lhomme <robux4@ycbcr.xyz>