patch 9.0.0036: 'fillchars' cannot have window-local values

Problem:    'fillchars' cannot have window-local values.
Solution:   Make 'fillchars' global-local. (closes #5206)
diff --git a/src/option.h b/src/option.h
index 815a115..5ac54ef 100644
--- a/src/option.h
+++ b/src/option.h
@@ -1238,6 +1238,7 @@
 {
     WV_LIST = 0
     , WV_LCS
+    , WV_FCS
 #ifdef FEAT_ARABIC
     , WV_ARAB
 #endif