Vocabulary entries are cut at 255 characters

[himselfv]

Original report by me.

This is because vocabularies are by format built without WORDFSIZE flag and dynamic
field sizes can be up to 255 bytes.

Proposed fix: set WORDFSIZE for all new vocabularies.
Cons:

• this'll make them incompatible with older Wakans
• existing vocabularies not fixed.

Proposed fix: wait until the planned vocabulary format upgrade (Issue 220) to avoid
doing the transition to new format twice.