Problem:
When buffer is open in multiple windows and its line count changes, any
'statusline' or 'rulerformat' items depending on it (e.g. %P) will
become invalid in non-current windows because w_redr_status is only set
on first change.
Solution:
Set w_redr_status on all windows with the buffer when the line count
changes.
Signed-off-by: Ondrej Balaz <blami@blami.net>