Alex just added this simple feature to Chibi:

(define-library-alias (scheme bitwise) (srfi 151))

Probably of interest to other Scheme implementations as well, especially
as R7RS-large re-exports a lot of SRFIs.

Diff at
<https://github.com/ashinn/chibi-scheme/commit/9901a67b202b649ce5037b3e2263bed4ff74c72f>.