per-file comments:
  mysql-test/r/gis.result
bug 855336      ST_LENGTH does not work on GEOMETRYCOLLECTIONs fixed.
        test result updated.
  mysql-test/t/gis.test
bug 855336      ST_LENGTH does not work on GEOMETRYCOLLECTIONs fixed.
        test case added.
  sql/item_geofunc.cc
bug 855336      ST_LENGTH does not work on GEOMETRYCOLLECTIONs fixed.
        geom_length() call fixed.
  sql/spatial.cc
bug 855336      ST_LENGTH does not work on GEOMETRYCOLLECTIONs fixed.
        Geometry_collection::geom_length implemented.
  sql/spatial.h
bug 855336      ST_LENGTH does not work on GEOMETRYCOLLECTIONs fixed.
        Geometry_collection::geom_length declaration added.