[Bf-committers] Updating bullet to 2.80

[Sergej Reich]

Hi all,

I'd like to update our local bullet code to the latest upstream version.
>From what I can tell it was last updated over a year ago and there were
two releases since then.
While they're mostly bug-fix releases as far as blender is concerned
there are still a couple of small features I'd like to have for my GSoC
project.
If there are no objections I'll figure out which local patches are still
needed and prepare a patch for review.

Regards, Sergej.