* Makefile.am (MODULES): Move guix/build/download-nar.scm to ...
(MODULES_NOT_COMPILED): ... here.
* guix/build/download-nar.scm: Use (zlib) instead of (guix zlib).
* guix/cvs-download.scm (cvs-fetch): Do not stub (guix config) in imported
modules list, instead add "guile-zlib" to the extension list.
* guix/git-download.scm (git-fetch): Ditto.
* guix/hg-download.scm (hg-fetch): Do not stub (guix config) in imported
modules list, instead add "guile-zlib" to the extension list.