[evolution-patches] patch for libdb

[Not Zed <notzed ximian com>]

I think we should apply these to our libdb at some point, at least, I
will almost certainly apply them to the disksummary branch soon, so just
letting anyone know who cares - which probably isn't anyone.

http://www.sleepycat.com/update/4.1.25/patch.4.1.25.html

I hit a strange problem where the performance suddenly died while
viewing large folders (2-3x slower), and this patch fixed it up.  Just
as well, I was in a sudden panic "oh boy this libdb thing can never be
fast enough, what have i done ..", etc!

(sigh, yes it is 4am again, blah & goodnight).