patch 9.0.0656: cannot specify another character to use instead of '@'

Problem:    Cannot specify another character to use instead of '@' at the end
            of the window.
Solution:   Add "lastline" to 'fillchars'. (Martin Tournoij, closes #11264,
            closes #10963)
diff --git a/src/optiondefs.h b/src/optiondefs.h
index 2ce3ec3..8a122ba 100644
--- a/src/optiondefs.h
+++ b/src/optiondefs.h
@@ -936,7 +936,8 @@
 			    SCTX_INIT},
     {"fillchars",   "fcs",  P_STRING|P_VI_DEF|P_RALL|P_ONECOMMA|P_NODUP,
 			    (char_u *)&p_fcs, PV_FCS,
-			    {(char_u *)"vert:|,fold:-,eob:~", (char_u *)0L}
+			    {(char_u *)"vert:|,fold:-,eob:~,lastline:@",
+								  (char_u *)0L}
 			    SCTX_INIT},
     {"fixendofline",  "fixeol", P_BOOL|P_VI_DEF|P_RSTAT,
 			    (char_u *)&p_fixeol, PV_FIXEOL,