patch 8.0.1289: mkview always includes the local directory

Problem:    Mkview always includes the local directory.
Solution:   Add the "curdir" value in 'viewoptions'. (Eric Roberts, closes
            #2316)
diff --git a/src/option.c b/src/option.c
index ceafea3..4f25c1f 100644
--- a/src/option.c
+++ b/src/option.c
@@ -2926,7 +2926,8 @@
     {"viewoptions", "vop",  P_STRING|P_VI_DEF|P_ONECOMMA|P_NODUP,
 #ifdef FEAT_SESSION
 			    (char_u *)&p_vop, PV_NONE,
-			    {(char_u *)"folds,options,cursor", (char_u *)0L}
+			    {(char_u *)"folds,options,cursor,curdir",
+								  (char_u *)0L}
 #else
 			    (char_u *)NULL, PV_NONE,
 			    {(char_u *)0L, (char_u *)0L}