Revert "Make dependencies target-specific"
Revert "Make dependencies target-specific"

This reverts commit 1188a3ffa6c2c254d5f38c80fdc5bf9847f6225a.

Although this change should happen at some point, that means dropping
support for older versions of Cargo. That means that this only works
with Cargo versions bundled with Rust 1.8 and later. I don't want to
force people into using such a recent version just yet.

ruud-v-a/filebuffer,ruuda/filebuffer