[Cooker] RC2: gabber overwrites archive files, not appends

[Damon Lynch]

Hi,

Gabber should be appending to it's archive, not overwriting what ever is
there.  RC2 Gabber keeps only the archive of the most recent chat,
instead of accumulating them by adding to the file as in 8.2 and 8.1
etc.

thanks!
Damon