lisp/*.el: Force non-nil result to t, to match docstring

lisp/*.el: Force non-nil result to t, to match docstring

* lisp/ido.el (ido-ignore-item-p):
* lisp/simple.el (use-region-p):
* lisp/whitespace.el (whitespace-style-face-p)
(whitespace-style-mark-p):
* lisp/calendar/cal-islam.el (calendar-islamic-leap-year-p):
* lisp/mail/rmail.el (rmail-is-text-p):
* lisp/mh-e/mh-alias.el (mh-alias-for-from-p):
* lisp/net/imap.el (imap-message-flag-permanent-p):
* lisp/progmodes/tcl.el (tcl-real-comment-p):
* lisp/textmodes/table.el (table--point-in-cell-p):
Normalize boolean result.