tmux: up the history limit by a factor of 8
tmux: up the history limit by a factor of 8

I just had a spec run that filled up the entire buffer with stack
traces... Checking the memory usage of tmux, I don't see any harm in
letting it retain more lines.

Signed-off-by: Wincent Colaiuta <c76ac2e9cd86441713c7dfae92c451f3e6d17fdc@wincent.com>

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent