Rollup merge of #39552 - zackmdavis:more_struct_aliases_stabilization_version, r...

correct version in which more_struct_aliases was/will be stable

The stabilizing commit is 5056a437, which is not in 1.14, but is (at
time of writing) on the 1.16 beta branch. [See discussion](https://github.com/rust-lang/rust/pull/39282#discussion_r99481687).

diff --cc src/libsyntax/feature_gate.rs
Simple merge