In this commit, we use exhaustive build tags to ensure that we can
always build the `sqlbase` package, independent of the set build tags.
To do this, we move the type declarations _into_ the parsing functions.
This then allows us to create two versions for each db: with the db, and
without it.
To avoid a module tag round trip to get this working, we use a local
replace for now. Once this is merged in, we can do the tag (along side
rc3), then remove the replace.
