(after discussion with SerG)


include/my_base.h:
  Handler error code added
myisam/mi_write.c:
  New error code handled
myisam/rt_index.c:
  check for zero length added
myisam/sp_key.c:
  zero length check added
mysql-test/r/gis-rtree.result:
  appropriate test result
mysql-test/t/gis-rtree.test:
  test case
sql/handler.cc:
  new error code handling added