fix for bug #801243 Assertion `(0)' failed in Gis_geometry_collection::init_from_opresult on ST_UNION 
        If the result contains a polygon with a hole, consequitive shapes weren't calculated
        properly, as the hole appeared as shape in the result, but actually it's a single shape
        with the surrounding polygon. It's more natural to use the size of the result as
        a border instead of the number of resulting shapes.

per-file comments:
  mysql-test/r/gis-precise.result
fix for bug #801243 Assertion `(0)' failed in Gis_geometry_collection::init_from_opresult on ST_UNION 
        test result updated.
  mysql-test/t/gis-precise.test
fix for bug #801243 Assertion `(0)' failed in Gis_geometry_collection::init_from_opresult on ST_UNION 
        test case added.
  sql/spatial.cc
fix for bug #801243 Assertion `(0)' failed in Gis_geometry_collection::init_from_opresult on ST_UNION 
        check the data lenght instead of number of shapes.
  sql/spatial.h
fix for bug #801243 Assertion `(0)' failed in Gis_geometry_collection::init_from_opresult on ST_UNION 
        check the data lenght instead of number of shapes.