two new window-matchers

[Christopher Roy Bratusek]

Hi all,

I just added two new window-matchers:
        - fixed-size
        - never-close

check ChangeLog/NEWS for more infos. For better user-experience of never-close, 
there's a
small change in the close-button keymap: now it calls `delete-window-safely' 
rather than
`delete-window'. (never-close only affects the former, but not the latter).

I don't think this change would hurt anyone...

Regards
Chris