customization type `vector'

[Drew Adams]

IIUC, customization type `vector', like type `list', can only be used for a
fixed number of elements. For lists, you can use `repeat' for a list with an
arbitrary number of elements, but I see no way to do this for vectors.

Is there some way, for instance, to specify that a value must be a vector of
characters? If not, is the only alternative to use `sexp' or
`restricted-sexp'?

If so, can this be remedied after the release? If not, what's the best that
could be done with, say, `restricted-sexp'? Would it be (restricted-sexp
:match-alternatives (vectorp))?

I'm thinking, for instance, of a :type that would fit a display-table
element, which must be either nil or a vector of characters.

Perhaps we could let `repeat' specify `list' or `vector'?