build-system/gnu: Pass --build=<triplet> to configure by default.

* guix/build-system/gnu.scm (gnu-build, gnu-cross-build): Accept #:build
  keyword argument.  Pass it to 'gnu-build' on the build side.
* guix/build/gnu-build-system.scm (configure): Accept #:build keyword
  argument.  Unless it is false, pass --build to configure.

gnu: perl: Do not retain references to Binutils and other build-time tools.

* gnu/packages/perl.scm (perl)[arguments]: Pass -Dlibpth and -Dplibpth to
  ./Configure.

packages: Rewrite 'transitive-inputs' to be linear and remove duplicates.

There were two issues:

  1. Use of 'delete-duplicates', which is quadratic, was a serious problem for
     closures with lots of propagated inputs, such as that of the 'hydra'
     package (several minutes for 'guix build hydra -n'!).

  2. The 'delete-duplicates' call essentially had no effect since duplicate
     inputs typically had a different label and were thus kept.  For
     instance, (bag-transitive-inputs (package->bag inkscape)) would return
     216 items whereas (delete-duplicates (map cdr THAT)) contains only 67
     items.

     The new implementation returns 67 items in this case.  For 'hydra', we're
     down from 42211 items to 361, and roughly 13s for 'guix build hydra'.

* guix/packages.scm (transitive-inputs): Rewrite as a breadth-first
  traversal.  Remove duplicate propagated inputs.
* tests/packages.scm ("package-transitive-inputs", "package->bag, propagated
  inputs"): Adjust to use simple labels for propagated inputs, without "/".
  ("package-transitive-inputs, no duplicates"): New test.

tests: Adjust tests for new bootstrap Guile.

This is a followup to commit 5d6792f ("gnu: bootstrap: Create a wrapper for
guile to set the system load path.")

* tests/size.scm ("store-profile"): Expect profile of 'bash' bootstrap binary.
* tests/gexp.scm ("gexp->derivation #:references-graphs"): Expect GUILE-DRV to
  depend on 'bash' bootstrap binary.

gnu: Require NEON on armhf.

* gnu/packages/gcc.scm (gcc-configure-flags-for-triplet): On armhf,
  include --with-fpu=neon.
* doc/guix.texi (GNU Distribution): Document that our armhf port
  requires NEON.

gnu: pcre: Enable more features.

* gnu/packages/pcre.scm (pcre)[arguments]: To configure-flags, add
  "--enable-unicode-properties", "--enable-pcre16", and "--enable-pcre32".

gnu: bash: Update to 4.3.39.

* gnu/packages/bash.scm (%patch-series-4.3): Add patches 34-39.

gnu: texinfo: Add procps to native-inputs to fix tests.

* gnu/packages/texinfo.scm (texinfo)[native-inputs]: Add procps.
  (texinfo-5, texinfo-4)[native-inputs]: Override to be empty.
* gnu/packages/commencement.scm (texinfo-boot0)[texinfo]: Override
  native-inputs to be empty.

gnu: nss: Update to 3.19.2.

* gnu/packages/gnuzilla.scm (nss): Update to 3.19.2.

gnu: libgpg-error: Update to 1.19.

* gnu/packages/gnupg.scm (libgpg-error): Update to 1.19.

gnu: libidn: Update to 1.31.

* gnu/packages/libidn.scm (libidn): Update to 1.31.

gnu: texinfo: Use version 6.0 by default.

* gnu/packages/texinfo.scm (texinfo): Update to 6.0.
  (texinfo-6): Removed.
  (texinfo-5): New variable.

gnu: libunistring: Update to 0.9.6.

* gnu/packages/libunistring.scm (libunistring): Update to 0.9.6.

gnu: mpfr: Update to 3.1.3.

* gnu/packages/multiprecision.scm (mpfr): Update to 3.1.3.

gnu: ed: Update to 1.12.

* gnu/packages/ed.scm (ed): Update to 1.12.

gnu: gettext: Update to 0.19.5.

* gnu/packages/patches/gettext-msgunfmt.patch: Remove file.
* gnu-system.am (dist_patch_DATA): Remove it.
* gnu/packages/gettext.scm (gnu-gettext): Update to 0.19.5.  Remove patch.

gnu: coreutils: Update to 8.24.

* gnu/packages/patches/coreutils-dummy-man.patch: Remove file.
* gnu-system.am (dist_patch_DATA): Remove it.
* gnu/packages/base.scm (coreutils): Update to 8.24.  Remove patch.

gnu: gcc-4.9: Update to 4.9.3.

* gnu/packages/gcc.scm (gcc-4.9): Update to 4.9.3.  Remove
  "gcc-arm-link-spec-fix.patch" from patches.

gnu: bootstrap: Create a wrapper for guile to set the system load path.

* gnu/packages/bootstrap.scm (raw-build): After unpacking, use the bootstrap
  guile to create its own wrapper that sets the guile system load path.

gnu: openssl: Update to 1.0.2d.

* gnu/packages/tls.scm (openssl): Update to 1.0.2d.