[RFC] vim-patch:7.4.285

Merging vim-patch:7.4.285

Problem:    When 'relativenumber' is set and deleting lines or undoing that,
            line numbers are not always updated. (Robert Arkwright)
Solution:   (Christian Brabandt)

https://code.google.com/p/vim/source/detail?r=5cb1828fd0056de3c166e71fbafc67a74c57d7b1