Remove some more reimplementations of cl-lib functions

Remove some more reimplementations of cl-lib functions

* lisp/doc-view.el: Require cl-lib at runtime too.
(doc-view-remove-if): Remove.
(doc-view-search-next-match, doc-view-search-previous-match):
Use cl-remove-if.

* lisp/edmacro.el: Require cl-lib at runtime too.
(edmacro-format-keys, edmacro-parse-keys): Use cl-mismatch, cl-subseq.
(edmacro-mismatch, edmacro-subseq): Remove.

* lisp/filesets.el: Comments.

* lisp/shadowfile.el: Require cl-lib.
(shadow-remove-if): Remove.
(shadow-set-cluster, shadow-shadows-of-1, shadow-remove-from-todo):
Use cl-remove-if.

* lisp/wid-edit.el: Require cl-lib.
(widget-choose): Use cl-remove-if.
(widget-remove-if): Remove.

* lisp/progmodes/ebrowse.el: Require cl-lib at runtime too.
(ebrowse-delete-if-not): Remove.
(ebrowse-browser-buffer-list, ebrowse-member-buffer-list)
(ebrowse-tree-buffer-list, ebrowse-same-tree-member-buffer-list):
Use cl-delete-if-not.