Increase allowable frame size again.

Certain encoders (especially on mobile devices, it seem) can still
generate somewhat larger files than we're seeing from most browsers.
This limit still puts us below average v1 GIF sizes at most, which we've
seen is fine for this server, and so shouldn't be a problem.
Merge pull request #80 from meatspaces/inc_filesize_more

Increase allowable frame size again.