The two following queries now become equivalent:

    vut -g request -q '
        # catch varnish errors
        *Error

        # catch backend errors
        BerespStatus >= 500
    '

    vut -g request -q '(*Error) or (BerespStatus >= 500)'

It becomes interesting when we wish to capture transactions for
different scenarios but would like to decompose them cleanly.
Especially when the query of an individual scenario is rather
complex and OR'ing everything manually would become cumbersome.

This diff is better viewed with the --ignore-all-space flag.