TPAC LDAP: include loc(g) param in login form

TPAC LDAP: include loc(g) param in login form

The "loc" CGI param has largely been supplanted by the "locg" CGI param.
In addition, we need to pass that parameter as part of the login
credentials, otherwise we always get the tip of the org_unit tree. There
may be other parameters we need to consider, as changing the search
location does not necessarily reflect the home library of the user in
question.

Perhaps a better approach would be to define a value in config.tt2 that
gets used here, so that sites with multiple skins & corresponding
authentication proxy setups can just configure config.tt2 on a per-skin
basis rather than having to override the entire login form.tt2?

Sprinkle some timelog messages around for the sake of checking
performance and debugging parameters.

Signed-off-by: Dan Scott <dscott@laurentian.ca>