Stable-Rust polyfill for unstable allocator_api: near-verbatim ports of std's Box/Vec/RawVec parameterised over Allocator. Three quality findings: medium (no active tests in the published crate despite extensive unsafe and a documented past Box::into_inner double-free fix), and two lows (empty CHANGELOG placeholder, published archive uses CRLF/CR while upstream uses LF — content byte-identical after normalisation).