After eliminating the minor differences in both files which existed
solely because features/fixes were applied to only one of them and not
the other, the remaining differences were in function naming and error
messages. The latter is addressed by using the 'id' field of struct
link_util.

Fold both files into one in order to share common code and eliminate the
chance of having fixes/enhancements applied to only one of them.
Signed-off-by: Phil Sutter <phil@nwl.cc>