Max compressed file size was calculated incorretly causing server
crash on INSERT.

With this patch we use proper max file size provided by zlib.

Affects 5.0 only.


sql/ha_archive.cc:
  When calculating max compressed file size, use the real offset size
  that is provided by zlib, instead of sizeof(z_off_t), which may be
  different from actual offset size.
  
  When we're about to write and the data file is almost full flush gzio
  buffer to get accurate real file size.
mysql-test/r/archive-big.result:
  New BitKeeper file ``mysql-test/r/archive-big.result''
mysql-test/t/archive-big.test:
  New BitKeeper file ``mysql-test/t/archive-big.test''