clarify choice value restrictions for select and select1

I think the only restriction is spaces for a select and for this reason strongly recommending to apply the same no-whitespace-restriction to select1 option values (so that a select1 could easily be changed into a select).

Start by locating the specification sections that define choice values for select and select1, then compare their stated whitespace restrictions and the issue's proposed alignment. Done means the specification clearly documents the restriction for both controls and records the intended rationale or resolution.

Written by the indexing model from the issue text.