Also now permit interactivly running tests without explicitly setting
$srcdir. This now works if we are inside ./tests and fails, as before,
when we are in a different directory.
Detected by shellcheck via CodeFactor.io
This adds support for endmsg.regex. It is similar to
startmsg.regex except that it matches the line that denotes
the end of the message, rather than the start of the next message.
This is primarily for container log file use cases such as this:
date stdout P start of message
date stdout P middle of message
date stdout F end of message
The `F` means this is the line which contains the final part of
the message. The fully assembled message should be
`start of message middle of message end of message`.
`startmsg.regex="^[^ ]+ stdout F "` will match.
