Squashed 'third-party/libuv/' content from commit 3c40224

git-subtree-dir: third-party/libuv
git-subtree-split: 3c4022464acd92607f21c6eef69330fb071d0400
Merge commit 'a302c65dc65896776d6cb9e2c89a6ccc77ada530' as 'third-party/libuv'
get-libuv.sh: compile bundled libuv

Rename file to reflect new intent of script. Libuv is bundled into the
third-party directory. Modify the script to compile but not fetch libuv.
Makefile: refer to renamed compile-libuv.sh

get-libuv.sh was renamed to compile-libuv.sh
third-party: add note on role of directory

Add a brief README on the purpose of the third-party directory and some
suggestions for how to manage it. The neovim bigwigs may want to
re-draft the README.
Merge branch 'bundle-libuv' of github.com:rjw57/neovim into rjw57-bundle-libuv