Make icomplete respect `completion-ignored-extensions'

* lisp/icomplete.el (icomplete-completions): Heed
`completion-ignored-extensions' (bug#12939).

etc/NEWS

@@ -56,6 +56,10 @@ affected by this, as SGI stopped supporting IRIX in December 2013.
 
 * Changes in Emacs 25.2
 
+---
+** icomplete now respects `completion-ignored-extensions'.
+
++++
 ** Non-breaking hypens are now displayed with the `nobreak-hyphen'
 face instead of the `escape-glyph' face.
 

lisp/icomplete.el

@@ -388,6 +388,9 @@ matches exist."
 	(progn ;;(debug (format "Candidates=%S field=%S" candidates name))
 	       (format " %sNo matches%s" open-bracket close-bracket))
       (if last (setcdr last nil))
+      (when (and minibuffer-completing-file-name
+                 icomplete-with-completion-tables)
+        (setq comps (completion-pcm--filename-try-filter comps)))
       (let* ((most-try
               (if (and base-size (> base-size 0))
                   (completion-try-completion