Hello,

As explained in gnatsweb.pl, the size of the query string is limited by the
browser to approx. 2K. That's why we want to strip the empty parameters.

This patch brings following changes to this:
- correct a bug where the striping was incorrect
- added a function to do the striping
- use that function everywhere, even where the striping was not done yet

With these changes, the URLs are now correct and as short as possible, even
in the return_url parameter.

This patch also removes the ability to store a query when the displayed
result is already the result of a stored query. This also leads to longer
query strings and could make the cookie unusable.

Regards
-- Alwin