Add function name to the ido list of S3 generics

ess-dbg-flag-for-debugging

There are some pseudo S3 generics like as.vector that don't really have
a as.vector.default.

git-svn-id: https://svn.r-project.org/ESS/trunk@5508 0bbaf3bd-34e0-0310-bf65-c717079852d4