runtime(doc): clarify the use of 'tagfunc', update a comment in tags.c

related: #17228

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index db7370d..6c60b58 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -8521,7 +8521,8 @@
 			local to buffer
 			{not available when compiled without the |+eval|
 			feature}
-	This option specifies a function to be used to perform tag searches.
+	This option specifies a function to be used to perform tag searches
+	(including |taglist()|).
 	The function gets the tag pattern and should return a List of matching
 	tags.  See |tag-function| for an explanation of how to write the
 	function and an example.  The value can be the name of a function, a