This bug is the result of weird error happening with mi_float8get and double
arythmetic. I described that in 'Bug that looks potentially dangerous' email


myisam/rt_mbr.c:
  *ab_area was changed with the local variable just to make the function
  working without errors
mysql-test/r/gis.result:
  appropriate test result
mysql-test/t/gis.test:
  Test case