gnu: hurd: Move configure flags from "hurd-minimal" to "hurd-headers".

* gnu/packages/hurd.scm (hurd-minimal)[arguments]: Move configure-flags from here..
  (hurd-headers)[arguments]: ..to here.

gnu: hurd: Remove inputs no longer needed.

* gnu/packages/hurd.scm (hurd-headers, hurd-minimal)[native-inputs]: Remove "autoconf".

gnu: hurd-headers: Use "--host=i586-pc-gnu" only when not cross-building.

* gnu/packages/hurd.scm (hurd-headers)[arguments]: Use "--host=i586-pc-gnu"
  only when not cross-building.

gnu: gnumach-headers: Use "--build=i586-pc-gnu" only when not cross-building.

* gnu/packages/hurd.scm (gnumach-headers)[arguments]: Use "--build=i586-pc-gnu"
  only when not cross-building.

gnu: base: Add glibc-for-target macro.

* gnu/packages/base.scm (glibc): Add macro.
  (glibc/linux): Rename glibc to glibc/linux.
  (glibc/hurd): Adjust accordingly.

gnu: libxml2: Upgrade to 2.9.4.

* gnu/packages/xml.scm (libxml2)[replacement]: Remove.
[version, source]: Upgrade to 2.9.4.
(libxml2/fixed): Remove.

Merge branch 'master' into core-updates

Revert "gnu: Default to GCC 5."

This reverts commit e3d0fcbf7e55e8cbe8d0a1c5a24d73f341d7243b.
This is a temporary measure until GCC 5 builds on ARM, see:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71399

bournish: Allow compilation of multiple expressions.

* guix/build/bournish.scm (%bournish-language): Add a joiner to SCHEME.
Compile only to Scheme.
* tests/bournish.scm: New file.
* Makefile.am (SCM_TESTS): Add it.

bournish: Handle EOF in the reader.

* guix/build/bournish.scm (read-bournish): Add case for EOF.

gnu: Add ghc-wl-pprint.

* gnu/packages/haskell.scm (ghc-wl-pprint): New variable.

gnu: Add ghc-union-find.

* gnu/packages/haskell.scm (ghc-union-find): New variable.

gnu: Add ghc-indents.

* gnu/packages/haskell.scm (ghc-indents): New variable.

gnu: Add ghc-concatenative.

* gnu/packages/haskell.scm (ghc-concatenative): New variable.

gnu: Add ghc-aeson-pretty.

* gnu/packages/haskell.scm (ghc-aeson-pretty): New variable.

file-systems: Remove unneeded import.

* gnu/system/file-systems.scm: Remove import of (guix gexp), unneeded
since commit 060d62a740fc1932a3be505534feff099b59ac9f.

gnu: glibc-hurd-headers: Use correct "--host".

* gnu/packages/base.scm (glibc/hurd-headers)[arguments]: Use "i586-pc-gnu"
  instead of "i686-pc-gnu".

gnu: glibc-hurd: Update to 20160518.

* gnu/packages/base.scm (glibc/hurd)[version]: Update to version 20160518.
  [propagated-inputs]: Use hurd-core-headers.
  [native-inputs]: Remove libpthread's source and "patch/libpthread-patch".
  [arguments]: Add augment-libc.so and pre-configure-set-pwd phases.
  Remove prepare-libpthread phase.  Stop removing "--with-headers="
  from original-configure-flags.
* gnu/packages/patches/glibc-hurd-extern-inline.patch: Remove patch.
* gnu/packages/patches/libpthread-glibc-preparation.patch: Likewise.
* gnu/local.mk (dist_patch_DATA): Remove them.

gnu: qtkeychain: Update to 0.7.0.

* gnu/packages/qt.scm (qtkeychain): Update to 0.7.0.

gnu: calibre: Update to 2.58.0.

* gnu/packages/ebook.scm (calibre): Update to 2.58.0.