vim-patch:7.4.277

Problem:    Using ":sign unplace *" may leave the cursor in the wrong position
            (Christian Brabandt)
Solution:   Update the cursor position when removing all signs.

https://code.google.com/p/vim/source/detail?r=373204662d82e894b27ee76bc3319bc62c91f6ae
Merge #744 'vim-patch:7.4.277'