enable by default blink-cusor-mode also on mac

[Emanuele Giaquinta]

'mac' is missing in the test on window-system to set the init-value of
blink-cursor-mode, add it.

Index: frame.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/frame.el,v
retrieving revision 1.228
diff -u -r1.228 frame.el
--- frame.el    6 Aug 2005 22:13:42 -0000       1.228
+++ frame.el    23 Sep 2005 15:09:59 -0000
@@ -1263,7 +1263,7 @@
   :init-value (not (or noninteractive
                       no-blinking-cursor
                       (eq system-type 'ms-dos)
-                      (not (memq window-system '(x w32)))))
+                      (not (memq window-system '(x w32 mac)))))
   :initialize 'custom-initialize-safe-default
   :group 'cursor
   :global t