gnu: guile-static: Add missing hunk in guile-default-utf8.patch.

Before that, the ‘guile’ binary from ‘guile-static-stripped’ would abort
as it tries and fails to open an iconv descriptor for ISO-8859-1.

* gnu/packages/patches/guile-default-utf8.patch: Add missing hunk for
  Guile 2.0.9.

distro: Change the module name space to (gnu ...).

* distro: Rename to...
* gnu: ... this.  Update module names accordingly.
* Makefile.am: Adjust accordingly.
* po/POTFILES.in: Likewise.
* distro.scm: Search for files under /gnu/packages instead of
  /distro/packages.
* gnu/packages/base.scm (ld-wrapper-boot3): Likewise.

build: Move `distro/patches' to `distro/packages/patches'.

* distro/patches: Move directory to...
* distro/packages/patches: ... here.
* Makefile.am (dist_patch_DATA): Adjust accordingly.
* pre-inst-env.in (DISTRO_PATCH_DIRECTORY): Likewise.

distro: Add patch to allow the bootstrap Guile to work without iconv.

* distro/patches/guile-default-utf8.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.

* distro/packages/base.scm (%guile-static): Use it.
  (%guile-static-stripped): Add call to `remove-store-references'.