Finally after 5 months! :)
Patch was already approved, but needed testing on existing files & time...
Description is here:
http://mediawiki.blender.org/index.php/BlenderDev/Transmissivity
In short: patch adds filtering based on thickness of material, and support
for internal reflection (resulting in better looking glass).
Thanks!
(Only note; appearance of glass render now differs... is acceptable, but for
the factor to control transmissivity a scaling factor could be added in UI,
the length of a ray is a relative thing...)
420b6ba5e4