org-agenda: Make `org-agenda-skip-(entry|subtree)-when.*' obsolete

* lisp/org-agenda.el (org-agenda-skip-entry-if):
(org-agenda-skip-entry-if):
(org-agenda-skip-entry-if): Move to...
* lisp/org-compat.el (org-agenda-skip-entry-when-regexp-matches):
(org-agenda-skip-subtree-when-regexp-matches):
(org-agenda-skip-entry-when-regexp-matches-in-subtree): ... here and
mark as obsolete.

These functions are not used in code base anymore, and they are easily
replaced with `org-agenda-skip-if'.

etc/ORG-NEWS

@@ -161,8 +161,21 @@ This allow to use a different title than entry title.
 ** Removed functions
 
 *** Org Timeline
+
 This feature has been removed.  Use a custom agenda view, possibly
 narrowed to current buffer to achieve a similar functionality.
+
+*** ~org-agenda-skip-entry-when-regexp-matches~ is obsolete
+
+Use ~org-agenda-skip-if~ instead.
+
+*** ~org-agenda-skip-subtree-when-regexp-matches~ is obsolete
+
+Use ~org-agenda-skip-if~ instead.
+
+*** ~org-agenda-skip-entry-when-regexp-matches-in-subtree~ is obsolete
+
+Use ~org-agenda-skip-if~ instead.
 ** Removed options
 
 *** ~org-agenda-repeating-timestamp-show-all~ is removed.

lisp/org-agenda.el

@@ -4775,43 +4775,6 @@ used by user-defined selections using `org-agenda-skip-function'.")
 This variable should not be set directly, but custom commands can bind it
 in the options section.")
 
-(defun org-agenda-skip-entry-when-regexp-matches ()
-  "Check if the current entry contains match for `org-agenda-skip-regexp'.
-If yes, it returns the end position of this entry, causing agenda commands
-to skip the entry but continuing the search in the subtree.  This is a
-function that can be put into `org-agenda-skip-function' for the duration
-of a command."
-  (let ((end (save-excursion (org-end-of-subtree t)))
-	skip)
-    (save-excursion
-      (setq skip (re-search-forward org-agenda-skip-regexp end t)))
-    (and skip end)))
-
-(defun org-agenda-skip-subtree-when-regexp-matches ()
-  "Check if the current subtree contains match for `org-agenda-skip-regexp'.
-If yes, it returns the end position of this tree, causing agenda commands
-to skip this subtree.  This is a function that can be put into
-`org-agenda-skip-function' for the duration of a command."
-  (let ((end (save-excursion (org-end-of-subtree t)))
-	skip)
-    (save-excursion
-      (setq skip (re-search-forward org-agenda-skip-regexp end t)))
-    (and skip end)))
-
-(defun org-agenda-skip-entry-when-regexp-matches-in-subtree ()
-  "Check if the current subtree contains match for `org-agenda-skip-regexp'.
-If yes, it returns the end position of the current entry (NOT the tree),
-causing agenda commands to skip the entry but continuing the search in
-the subtree.  This is a function that can be put into
-`org-agenda-skip-function' for the duration of a command.  An important
-use of this function is for the stuck project list."
-  (let ((end (save-excursion (org-end-of-subtree t)))
-	(entry-end (save-excursion (outline-next-heading) (1- (point))))
-	skip)
-    (save-excursion
-      (setq skip (re-search-forward org-agenda-skip-regexp end t)))
-    (and skip entry-end)))
-
 (defun org-agenda-skip-entry-if (&rest conditions)
   "Skip entry if any of CONDITIONS is true.
 See `org-agenda-skip-if' for details."

lisp/org-compat.el

@@ -295,6 +295,47 @@ You could use brackets to delimit on what part the link will be.
  "set `:sitemap-format-entry' in `org-publish-project-alist' instead."
  "Org 9.1")
 
+(defvar org-agenda-skip-regexp)
+(defun org-agenda-skip-entry-when-regexp-matches ()
+  "Check if the current entry contains match for `org-agenda-skip-regexp'.
+If yes, it returns the end position of this entry, causing agenda commands
+to skip the entry but continuing the search in the subtree.  This is a
+function that can be put into `org-agenda-skip-function' for the duration
+of a command."
+  (declare (obsolete "use `org-agenda-skip-if' instead." "Org 9.1"))
+  (let ((end (save-excursion (org-end-of-subtree t)))
+	skip)
+    (save-excursion
+      (setq skip (re-search-forward org-agenda-skip-regexp end t)))
+    (and skip end)))
+
+(defun org-agenda-skip-subtree-when-regexp-matches ()
+  "Check if the current subtree contains match for `org-agenda-skip-regexp'.
+If yes, it returns the end position of this tree, causing agenda commands
+to skip this subtree.  This is a function that can be put into
+`org-agenda-skip-function' for the duration of a command."
+  (declare (obsolete "use `org-agenda-skip-if' instead." "Org 9.1"))
+  (let ((end (save-excursion (org-end-of-subtree t)))
+	skip)
+    (save-excursion
+      (setq skip (re-search-forward org-agenda-skip-regexp end t)))
+    (and skip end)))
+
+(defun org-agenda-skip-entry-when-regexp-matches-in-subtree ()
+  "Check if the current subtree contains match for `org-agenda-skip-regexp'.
+If yes, it returns the end position of the current entry (NOT the tree),
+causing agenda commands to skip the entry but continuing the search in
+the subtree.  This is a function that can be put into
+`org-agenda-skip-function' for the duration of a command.  An important
+use of this function is for the stuck project list."
+  (declare (obsolete "use `org-agenda-skip-if' instead." "Org 9.1"))
+  (let ((end (save-excursion (org-end-of-subtree t)))
+	(entry-end (save-excursion (outline-next-heading) (1- (point))))
+	skip)
+    (save-excursion
+      (setq skip (re-search-forward org-agenda-skip-regexp end t)))
+    (and skip entry-end)))
+
 ;;;; Obsolete link types
 
 (eval-after-load 'org