deps: upgrade libuv to e89aced
test: re-enable simple/test-setproctitle on darwin

The functionality is available again per joyent/libuv@14eb8b0
and joyent/libuv@e89aced.

Fixes #3687.
crypto: fix base64 padding regression

Commit 9901b69c introduces a small regression where the trailing base64
padding is no longer written out when Cipher#final is called. Rectify
that.

Fixes #4837.