Clarify `mark-ring-max' documentation.

* mark.texi (Mark Ring): Clarify how many locations are saved
(bug#5770).
(Global Mark Ring): Ditto.

doc/emacs/ChangeLog

+2011-07-13  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+	* mark.texi (Mark Ring): Clarify how many locations are saved
+	(bug#5770).
+	(Global Mark Ring): Ditto.
+
 2011-07-12  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
 	* text.texi (Table Recognition): Use "at point" instead of "under

doc/emacs/mark.texi

@@ -253,7 +253,9 @@ Another effect of this mode is that some keys, such as @key{DEL} and
 @cindex mark ring
   Aside from delimiting the region, the mark is also useful for
 remembering spots that you may want to go back to.  Each buffer
-remembers 16 previous locations of the mark, in the @dfn{mark ring}.
+remembers @code{mark-ring-max} previous locations of the mark, in the
+@dfn{mark ring}.  This defaults to 16 locations.
+
 Commands that set the mark also push the old mark onto this ring.
 
 @table @kbd
@@ -315,10 +317,12 @@ Positions in Registers}).
 @section The Global Mark Ring
 @cindex global mark ring
 
+@vindex global-mark-ring-max
   In addition to the ordinary mark ring that belongs to each buffer,
 Emacs has a single @dfn{global mark ring}.  Each time you set a mark,
 in any buffer, this is recorded in the global mark ring in addition to
-the current buffer's own mark ring.
+the current buffer's own mark ring.  The length of this ring can be
+controlled by @code{global-mark-ring-max}, and is 16 by default.
 
 @kindex C-x C-@key{SPC}
 @findex pop-global-mark