we didn't have code creating GEOMETRY-type fields from Items (expression results)
So i added this code


mysql-test/r/gis.result:
  test result fixed
mysql-test/t/gis.test:
  testcase added
sql/item_geofunc.cc:
  Item_geometry_func::tmp_table_field implemented
sql/item_geofunc.h:
  tmp_table_field() and get_geometry_type() declared