Archive engine returns wrong values for average record length
and max data length.

With this fix they're calculated as following:
- max data length is 2 ^ 63 where large files are supported
  and INT_MAX32 where this is not supported;
- average record length is data length / records in data file.

mysql-test/r/archive.result:
  A test case for BUG#29203.
mysql-test/t/archive.test:
  A test case for BUG#29203.
storage/archive/ha_archive.cc:
  Better estimation for average row length and maximal data
  file length.