* guix/derivations.scm (sha256): Rewrite using libchop's `bytevector-hash'. (derivation-hash): Add docstring.
* guix/derivations.scm: Export `read-derivation' and `write-derivation'. * srfi/srfi-64.scm, srfi/srfi-64.upstream.scm: New files, from libchop. * tests/derivations.scm, tests/test.drv: New files.
* guix.scm: Move contents to other files. Just aggregate these. * guix/derivations.scm, guix/store.scm: New files.