[Xastir] More bugs fixed

[Curt, WE7U]

Fixed another couple of bugs:

*) Sometimes positions from the object.log file were skipped on
startup.  The place where that file and the CAD_objects file are
read in has moved from main() to UpdateTime(), after create_image()
has been called.  This fixed it.

*) If the viewport spanned two UTM zones, the Xastir
terraserver/toposerver code would refuse to even try to download a
map.  Now it snags a map which fits one zone or the other.  Since
terraserver is based on UTM zones, this is as good as it gets, at
least until someone decides to implement this:

    1) Check whether zstr0 != zstr1.
    2) If so, do _two_ map fetches, one for each zone.
    3) Draw each of these two maps into the pixmap only up to the
       UTM zone line so that they tile together nicely.

I added some comments to the sources and submitted a feature request
for this.

I suppose the idea could be extended to cover multiple zones (more
than two) as well, but I can't see a real need for that:  The maps
would be zoomed too far out to be useful.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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