* jt/subprocess-handshake:
sub-process: refactor handshake to common function
Documentation: migrate sub-process docs to header
convert: add "status=delayed" to filter process protocol
convert: refactor capabilities negotiation
convert: move multiple file filter error handling to separate function
convert: put the flags field before the flag itself for consistent style
t0021: write "OUT <size>" only on success
t0021: make debug log file name configurable
t0021: keep filter log files on comparison