cargo: fix version in features chain

This fixes the definition of the `v2016_4` feature.
It restores the chain of versions so that 2016.3 symbols can be
actually reached from newer features/versions.

rust-bindings/rust/Cargo.toml

@@ -56,7 +56,7 @@ dox = ["ffi/dox"]
 v2014_9 = ["ffi/v2014_9"]
 v2015_7 = ["v2014_9", "ffi/v2015_7"]
 v2016_3 = ["v2015_7", "ffi/v2016_3"]
-v2016_4 = ["v2015_7", "ffi/v2016_4"]
+v2016_4 = ["v2016_3", "ffi/v2016_4"]
 v2016_5 = ["v2016_4", "ffi/v2016_5"]
 v2016_6 = ["v2016_5", "ffi/v2016_6"]
 v2016_7 = ["v2016_6", "ffi/v2016_7"]