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/testdir/screendump.vim b/src/testdir/screendump.vim
index d872a80..e19d4f5 100644
--- a/src/testdir/screendump.vim
+++ b/src/testdir/screendump.vim
@@ -75,6 +75,8 @@
 	endif
       else
 	let msg = 'See new dump file: call term_dumpload("testdir/' .. testfile .. '")'
+	" no point in retrying
+	let g:run_nr = 10
       endif
       for i in range(len(refdump))
 	if i >= len(testdump)