[RFC] vim-patch:7.4.218

Problem:  It's not easy to remove duplicates from a list.

Solution: Add the uniq() function. (LCD)

https://code.google.com/p/vim/source/detail?r=ddc3f32a4b2191f829206322d46f0e9c7e365e22

(I'll make the changes to `version.c` when rebasing, depending on which patches were merged by then.)