Enable nquery mode to normalize requested extent (like drawing does)

[sdlime]

When folks are using the [shpxy ...] tag to produce image maps you want the
extent used to query MapServer to match the image produced via the query map.
The solution is to introduce a new CGI parameter called "adjust" and if set with
certain query modes the submitted extent would be adjusted BEFORE the query is
done. A relatively minor addition (actually MapServer used to have this option
way back...).

Steve

[sdlime]

Turns out that option (searchmap) is still in the code so there's no need to do
anything.

Steve