* guix/build/utils.scm (substitute): Change to accept a `pattern+procs'
parameter. Iterate over it.
(substitute*): Adjust accordingly.
* distro/base.scm (guile-1.8): Adjust accordingly.
* guix/build/utils.scm (let-matches, substitute*): New macros.
* distro/base.scm (guile-1.8): Use `substitute*' instead of
`substitute'. Remove the #:modules argument.
* guix/packages.scm (<package-source>): Rename to...
(<origin>): ... this. Update users.
* distro/base.scm (libsigsegv, gawk, hello): Adjust to renaming; refer
to VERSION to build the URL.
* guix/packages.scm (package-derivation): When ARGS is a procedure, call
(ARGS SYSTEM).
* distro/base.scm (gawk)[arguments]: Turn into a procedure, to disable
tests on Cygwin.
* guix/packages.scm (<package>)[arguments]: Default to '().
* distro/base.scm (libsigsegv, gawk): New packages.
(hello): Use GAWK instead of (nixpkgs-derivation "gawk").
* Makefile.am (MODULES): Add `guix/packages.scm' and `distro/base.scm'.
(TESTS): Add `tests/packages.scm'.
(EXTRA_DIST): New variable.
* guix/packages.scm, distro/base.scm, tests/packages.scm: New files.
* guix/http.scm (http-fetch): Make `name' an optional argument, to match
the expectations of `package-source-derivation'.
Ludovic Courtès