The function mi_get_pointer_length() computed too small
pointer size for very large tables.

Inserted missing 'else' between the branches for very
large tables.


myisam/mi_create.c:
  Bug#24607 - MyISAM pointer size determined incorrectly
  Inserted missing 'else' between the branches for very
  large tables.
  Harmonized literals "(longlong) 1" and "1L" to "ULL(1)"
  where they are used for "ulonglong file_length".
mysql-test/r/myisam.result:
  Bug#24607 - MyISAM pointer size determined incorrectly
  Added the test result.
mysql-test/t/myisam.test:
  Bug#24607 - MyISAM pointer size determined incorrectly
  Added the test.