vim-patch:7.4.320

Problem:    Possible crash when an BufLeave autocommand deletes the buffer.
Solution:   Check for the window pointer being valid.  Postpone freeing the
            window until autocommands are done. (Yasuhiro Matsumoto)

https://code.google.com/p/vim/source/detail?r=v7-4-320
Merge pull request #1209 from atwupack/vp-7.4.320

vim-patch:7.4.320