Closing as this is already solved.

r-devel/r-dev-day#76

Kurt committed a variant of this patch in revision SVN r87570 with a small tweak today. He says:

I just committed a variant of the patch with c87570. Unfortunately, I
managed to commit too much in one commit, so the commit msg does not
give credit etc. Sorry.

The change looks a bit different as I re-used and enhanced exisiting
code, ensured to match PKG::.Deprecated and PKG::.Defunct when PKG is
base but not otherwise, and changed to filter at the end as ideally we
do get() calls to get the functions from their names as little as
possible.