* sly.el (sly-warning): Renamed from `sly-display-warning'

* contrib/sly-fontifying-fu.el (sly-search-suppressed-forms)
(sly-extend-region-for-font-lock): Use new `sly-warning'

* contrib/sly-mrepl.el (sly-mrepl--commit-buffer-name): Use new
`sly-warning'.