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/structs.h b/src/structs.h
index a537ccb..11c3726 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -232,6 +232,8 @@
 #define w_p_list w_onebuf_opt.wo_list	// 'list'
     char_u	*wo_lcs;
 #define w_p_lcs w_onebuf_opt.wo_lcs	// 'listchars'
+    char_u	*wo_fcs;
+#define w_p_fcs w_onebuf_opt.wo_fcs	// 'fillchars'
     int		wo_nu;
 #define w_p_nu w_onebuf_opt.wo_nu	// 'number'
     int		wo_rnu;
@@ -3419,6 +3421,22 @@
 } lcs_chars_T;
 
 /*
+ * Characters from the 'fillchars' option
+ */
+typedef struct
+{
+    int	stl;
+    int	stlnc;
+    int	vert;
+    int	fold;
+    int	foldopen;
+    int	foldclosed;
+    int	foldsep;
+    int	diff;
+    int	eob;
+} fill_chars_T;
+
+/*
  * Structure which contains all information that belongs to a window
  *
  * All row numbers are relative to the start of the window, except w_winrow.
@@ -3470,6 +3488,7 @@
 					 // redrawn
 
     lcs_chars_T	w_lcs_chars;	    // 'listchars' characters
+    fill_chars_T w_fill_chars;	    // 'fillchars' characters
 
     /*
      * "w_topline", "w_leftcol" and "w_skipcol" specify the offsets for