Reference identifiers instead of "above" in code comments as these
tends to become outdated. Even when declarations are removed it's at
least clear that the reference no longer exists instead of referring to
whatever is currently above the declaration.
It's also straightforward to search history for a removed identifier.
Corrected 4 cases of references to things that were no longer above
the doc-strings. Noticed other references which look to be incorrect
but need further investigation.
7632c528de