closedcaption/sccparse: Don't strictly require empty lines between each caption line
closedcaption/sccparse: Don't strictly require empty lines between each caption line

There is some broken software out there not inserting the empty lines
and we don't really need them for proper parsing. Only require an empty
line between header and the first caption line.

sdroege/rsplugin,sdroege/rsplugin