Isolate references to versioning
Currently, we have versioning references in hard-coded strings in a couple places around the codebase. For example, in protover.c and dirserv.c
It would be useful to isolate these references to a single location, so that in the future, when we need to update/change versions, it is obvious all the places that we might need to do it, and what duplication already exists.
This will hopefully help prevent bugs such as legacy/trac#20810 (moved) in the future.