distro: Rebuild bootstrap Binutils and GCC.

These new binaries are built with the `--with-lib-path' and
`--with-local-prefix' flags, respectively, as introduced in commit
01d4540.

* distro/packages/bootstrap.scm (%bootstrap-coreutils&co,
  %bootstrap-glibc): Update URL.
  (%bootstrap-binutils, %bootstrap-gcc): Update URL and hashes.
* build-aux/download.scm (file-name->uri): Update URL.

distro: Configure ld and GCC to not look under /usr & co.

This fixes impurities with non-chroot builds on LFS-style distros.

* distro/packages/base.scm (binutils): Pass `--with-lib-path'.
  (gcc-4.7): Pass `--with-local-prefix'.
* distro/packages/make-bootstrap.scm (%binutils-static): Pass
  `--with-lib-path'.

distro: Add GNU Texinfo.

* distro/packages/texinfo.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add GNU Libtasn1 and GnuTLS.

* distro/packages/gnutls.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add GNU Nettle.

* distro/packages/nettle.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add LZO.

* distro/packages/compression.scm (lzo): New variable.

distro: Patch libc to avoid accessing /etc/ld.so.cache and friends.

* distro/packages/base.scm (glibc): Apply `glibc-no-ld-so-cache.patch'.
  (glibc-final): Inherit GLIBC's inputs.
* distro/packages/patches/glibc-no-ld-so-cache.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.

distro: Use `mirror://' URLs.

* distro/packages/base.scm, distro/packages/bash.scm,
  distro/packages/compression.scm, distro/packages/gawk.scm,
  distro/packages/gperf.scm, distro/packages/guile.scm,
  distro/packages/libsigsegv.scm, distro/packages/libtool.scm,
  distro/packages/libunistring.scm, distro/packages/m4.scm,
  distro/packages/multiprecision.scm, distro/packages/ncurses.scm,
  distro/packages/pth.scm, distro/packages/readline.scm,
  distro/packages/recutils.scm: Use `mirror://gnu' URLs.
* distro/packages/gnupg.scm: Use `mirror://gnupg' URLs.

Remove (guix http) and (guix ftp).

* guix/ftp.scm, guix/http.scm, guix/build/ftp.scm, guix/build/http.scm:
  Remove.
* Makefile.am (MODULES): Likewise.
* tests/builders.scm, distro/packages/base.scm,
  distro/packages/bash.scm, distro/packages/bdw-gc.scm,
  distro/packages/compression.scm, distro/packages/gawk.scm,
  distro/packages/gnupg.scm, distro/packages/gperf.scm,
  distro/packages/guile.scm, distro/packages/libffi.scm,
  distro/packages/libsigsegv.scm, distro/packages/libtool.scm,
  distro/packages/libunistring.scm, distro/packages/lout.scm,
  distro/packages/m4.scm, distro/packages/multiprecision.scm,
  distro/packages/ncurses.scm, distro/packages/perl.scm,
  distro/packages/pkg-config.scm, distro/packages/pth.scm,
  distro/packages/readline.scm, distro/packages/recutils.scm: Use
  `url-fetch' instead of `http-fetch' and `ftp-fetch'.
* distro/packages/bootstrap.scm: Likewise
  (bootstrap-origin): Remove references to `http-fetch' and
  `ftp-fetch'.
* guix.scm (%public-modules): Remove `http' and `ftp'; add `download'.

Add (guix download) and (guix build download).

* guix/download.scm, guix/build/download.scm: New files.
* Makefile.am (MODULES): Add them.
* tests/builders.scm ("url-fetch"): New test.
* distro/packages/bootstrap.scm (bootstrap-origin): Support
  `url-fetch'.
* guix/snix.scm (snix-derivation->guix-package): Use `url-fetch' instead
  of `http-fetch'.

distro: Move bootstrap tarball packages to (distro packages make-bootstrap).

* distro/packages/base.scm (binutils-final): Make public.
  (static-package, %bash-static, %static-inputs, %static-binaries,
  %binutils-static, %binutils-static-stripped, %glibc-stripped,
  %gcc-static, %gcc-stripped, %guile-static, %guile-static-stripped,
  tarball-package, %bootstrap-binaries-tarball,
  %binutils-bootstrap-tarball, %glibc-bootstrap-tarball,
  %guile-bootstrap-tarball): Move to...
* distro/packages/make-bootstrap.scm: ... here.  New file.
* Makefile.am (MODULES): Add it.

distro: bash-final: Link with `-static-libgcc'.

* distro/packages/base.scm (bash-final): Pass through
  `static-libgcc-package'.

distro: gcc: Don't add a RUNPATH to GCC when using `-static-libgcc'.

* distro/packages/base.scm (gcc-4.7)[LIB_SPEC]: Add a `-rpath' to GCC
  only when !static and !static-libgcc.

distro: readline: Allow stripping of the libraires.

* distro/packages/readline.scm (readline)[arguments]: Add `post-install'
  phase to make libraries writable.

utils: Add `default-keyword-arguments' and `substitute-keyword-arguments'.

* distro/packages/base.scm (default-keyword-arguments,
  substitute-keyword-arguments): Move to...
* guix/utils.scm: ... here.

distro: Add missing `package-with-bootstrap-guile'.

* distro/packages/base.scm (binutils-final): Add missing
  `package-with-bootstrap-guile'.

distro: recutils: Comment out optional dependencies.

* distro/packages/recutils.scm (recutils): Comment out optional
  dependencies not packaged here.

distro: Add GnuPG and companion libraries.

* distro/packages/gnupg.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add zlib.

* distro/packages/compression.scm (zlib): New variable.

distro: Add (distro packages compression).

* distro/packages/base.scm (gzip, bzip2, xz): Move to...
* distro/packages/compression.scm: ... here.  New file.
* Makefile.am (MODULES): Add it.