* lisp/replace.el (query-replace-from-to-separator): Turn defvar into defcustom.
Wrap char-displayable-p in ignore-errors because an attempt
to autoload char-displayable-p fails during pre-loading.
Move (propertize "\0" ... 'separator t) out of customizable part
to query-replace-read-from.
(query-replace-read-from): Call custom-reevaluate-setting on
query-replace-from-to-separator to reevaluate the separator
depending on the return value of char-displayable-p.
http://lists.gnu.org/archive/html/emacs-devel/2014-11/msg00466.html