ediff: use user-error rather than debug-ignored-errors

ediff: use user-error rather than debug-ignored-errors

* lisp/vc/ediff-diff.el (ediff-prepare-error-list):
* lisp/vc/ediff-help.el (ediff-help-for-quick-help):
* lisp/vc/ediff-init.el (ediff-barf-if-not-control-buffer)
(ediff-check-version):
* lisp/vc/ediff-merg.el (ediff-shrink-window-C):
* lisp/vc/ediff-mult.el (ediff-draw-dir-diffs, ediff-show-dir-diffs)
(ediff-append-custom-diff, ediff-meta-show-patch)
(ediff-filegroup-action, ediff-show-meta-buffer, ediff-show-registry)
(ediff-get-meta-info, ediff-patch-file-form-meta):
* lisp/vc/ediff-ptch.el (ediff-patch-file-internal):
* lisp/vc/ediff-util.el (ediff-toggle-autorefine)
(ediff--check-ancestor-exists, ediff-toggle-read-only)
(ediff-toggle-wide-display, ediff-toggle-multiframe)
(ediff-toggle-use-toolbar, ediff-toggle-show-clashes-only)
(ediff-next-difference, ediff-previous-difference)
(ediff-pop-diff, ediff-read-file-name, ediff-verify-file-buffer)
(ediff-save-buffer):
* lisp/vc/ediff-wind.el (ediff-make-wide-display):
* lisp/vc/ediff.el (ediff-find-file, ediff-buffers-internal)
(ediff-directories-internal, ediff-directory-revisions-internal)
(ediff-regions-wordwise, ediff-regions-linewise)
(ediff-load-version-control): Use user-error.
(debug-ignored-errors): No longer modify.