* srfi/srfi-64.upstream.scm [guile]: Remove use of (ice-9 syntax-case).
* 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.