Added support for better merging of height fields which ignores NoData

values.  Fixed various problems with handing of coordinates systems. Added
support for halving levels in x and y respectively, in addition to the
previous divide in both x and y at the same time, which allows long
line/short tall regions to be handled better.

examples/osgdem/osgdem.cpp

@@ -115,7 +115,7 @@ int main( int argc, char **argv )
     }
 
 
-    if (false)
+    if (true)
     {
         // set up the coordinate system
         OGRSpatialReference     oSRS;