Update vim-eiffel

the upstream repo has not been updated since 2016. So I forked this repo, and merge pull request. this repo is for [SpaceVim](https://spacevim.org) `lang#eiffel` layer.

1. add compiler

based on @dkearns's pull request: https://github.com/eiffelhub/vim-eiffel/pull/3

2. syntax file,

in https://github.com/eiffelhub/vim-eiffel/pull/4 