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

Problem:    'fillchars' cannot have window-local values.
Solution:   Make 'fillchars' global-local. (closes vim/vim#5206)
96ba25ac01

Cherry-pick g:run_nr from patch 8.2.0454.

N/A patches for version.c:

vim-patch:9.0.0037: build error

Problem:    Build error.
Solution:   Add missing change.
510f03738d

src/nvim/mbyte.c

@@ -1989,8 +1989,7 @@ theend:
 }
 
 /// @return  true if string "s" is a valid utf-8 string.
-/// When "end" is NULL stop at the first NUL.
-/// When "end" is positive stop there.
+/// When "end" is NULL stop at the first NUL.  Otherwise stop at "end".
 bool utf_valid_string(const char_u *s, const char_u *end)
 {
   const char_u *p = s;