Auto merge of rust-lang#28608 - eddyb:no-place-for-an-old-box, r=pnkf…

…elix

While this is technically a [breaking-change], there is no excuse for touching `HEAP`.
r? @pnkfelix

1.3.0 release

1.2.0 release

1.1.0 release

1.0.0 release

1.0.0-alpha.2 release

1.0.0-alpha release

0.12.0 release

0.11.0 release