vim-patch:7.4.456

Problem:  'backupcopy' is global, cannot write only some
          files in a different way.
Solution: Make 'backupcopy' global-local. (Christian Brabandt)

https://code.google.com/p/vim/source/detail?r=v7-4-456
Merge pull request #1712 from fwalch/vim-7.4.456

vim-patch:7.4.456