privoxy-regression-test: Add a --privoxy-cgi-prefix option
... that specifies the prefix to use when building URLs that are
supposed to reach Privoxy's CGI interface. If it's not set,
http://p.p/ is used, which is supposed to work with the default
Privoxy configuration.
If Privoxy has been built with FEATURE_HTTPS_INSPECTION enabled,
and if https inspection is activated with the +https-inspection
action, this option can be used with "https://p.p/" provided the
system running Privoxy-Regression-Test has been configured to
trust the certificate used by Privoxy.
Note that there are currently two tests in the official
regression-tests.action file that are expected to fail
when using "https://p.p/" as privoxy-cgi-prefix.