Fix search by GPS coordinates

ImageSearchInfo::setRegionSelection failed to increase the
m_matchGeneration, thus causing incorrect/stale search results. In the
words of Reimar Imhof:

I like the geo position feature in kphotoalbum.
Now I ran in this gps select/search issue:
1.) Select places, select a place --> all pictures tagged with that place are
selected. That's expected. (Or you could select people or what ever.)
2.) Go to geo position and select some of the selected pictures by gps
position. --> the selection doesn't change. That's not expected.

My patch is very simple:
In ImageSearchInfo I've seen a call to

m_matchGeneration = nextGeneration()

every time the search info is changed. As I couldn't find this call to
nextGeneration() when setting the gps region (setRegionSelection(...)), I've
just changed this.
Now I can select pictures by gps position even if I've allready selected by
some categories or even gps positions.

Thanks Reimar for the patch!