checksum)"

The problem was that checksum of GEOMETRY type used memory addresses
in the computation, making it un-repeatable thus useless.
(This patch is a backport from 6.0 branch)

mysql-test/r/myisam.result:
  test case for bug35570 that same tables give same checksums
mysql-test/t/myisam.test:
  test case for bug35570 that same tables give same checksums
sql/sql_table.cc:
  Type GEOMETRY is implemented on top of type BLOB, so, just like for BLOB,
  its 'field' contains pointers which it does not make sense to include in
  the checksum; it rather has to be converted to a string and then we can
  compute the checksum.