Use obarrayp, not vectorp, to detect obarrays

Use obarrayp, not vectorp, to detect obarrays

* lisp/abbrev.el (abbrev--active-tables):
* lisp/mail/mailabbrev.el (mail-abbrevs-setup, build-mail-abbrevs)
(define-mail-abbrev, mail-resolve-all-aliases)
(mail-abbrev-insert-alias):
* lisp/mail/rmail.el (rmail-resend):
* lisp/minibuffer.el (completion-table-with-context):
* lisp/progmodes/etags.el (etags-tags-apropos-additional):
(etags--xref-apropos-additional):
Use obarrayp as predicate for obarrays.