patch 8.1.0864: cannot have a local value for 'scrolloff' and 'sidescrolloff'

Problem:    Cannot have a local value for 'scrolloff' and 'sidescrolloff'.
            (Gary Holloway)
Solution:   Make 'scrolloff' and 'sidescrolloff' global-local. (mostly by
            Aron Widforss, closes #3539)
diff --git a/src/structs.h b/src/structs.h
index ddc56bc..e6cc829 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2932,6 +2932,8 @@
     int		w_p_brishift;	    /* additional shift for breakindent */
     int		w_p_brisbr;	    /* sbr in 'briopt' */
 #endif
+    long        w_p_siso;           /* 'sidescrolloff' local value */
+    long        w_p_so;             /* 'scrolloff' local value */
 
     /* transform a pointer to a "onebuf" option into a "allbuf" option */
 #define GLOBAL_WO(p)	((char *)p + sizeof(winopt_T))