Remove unused patchelf inputs.

* gnu/packages/maths.scm (lapack, gmsh), gnu/packages/ssh.scm (libssh): Remove
  unused patchelf from native-inputs.

gnu: bigloo: Use Emacs with X11 support.

* gnu/packages/scheme.scm (bigloo)[inputs]: Change EMACS-NO-X to EMACS.

gnu: sdl: Explicitly use mesa as OpenGL driver.

* gnu/packages/sdl.scm (sdl)[arguments]<#:configure-flags>: Add
  'LDFLAGS=-lGL'.

gnu: sdl: Allow dlopen for OpenGL.

Fixes a regression introduced in 666aa99.
Reported by Felipe López and David Thompson.

* gnu/packages/sdl.scm (sdl)[inputs]: Add glu.
  [arguments]<#:configure-flags>: Replace '--disable-sdl-dlopen' with
  '--disable-alsa-shared --disable-pulseaudio-shared --disable-x11-shared'.

gnu: Add python-h5py and python2-h5py.

* gnu/packages/python.scm (python-h5py, python2-h5py): New variables.

gnu: Add Julia.

* gnu/packages/julia.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

gnu: Add double-conversion.

* gnu/packages/maths.scm (double-conversion): New variable.

gnu: Add SuiteSparse.

* gnu/packages/maths.scm (suitesparse): New variable.

gnu: icedtea6: remove commented substitution.

* gnu/packages/java.scm (icedtea6): Remove commented substitution.

gnu: icedtea6: Do not set CC and LD_LIBRARY_PATH.

* gnu/packages/java.scm (icedtea6)[arguments]: Do not set CC and
  LD_LIBRARY_PATH variables.

gnu: icedtea6: Rename ‘set-paths’ phase to ‘set-additional-paths’

* gnu/packages/java.scm (icedtea6)[arguments]: Rename ‘set-paths’ phase to
  ‘set-additional-paths’.

gnu: icedtea6: patch patches in separate build phase.

* gnu/packages/java.scm (icedtea6)[arguments]: Move patching of patches from
  ‘patch-paths’ to new ‘patch-patches’ phase.

gnu: icedtea6: patch hardcoded objcopy path.

* gnu/packages/java.scm (icedtea6)[arguments]: patch Makefile to override
  DEF_OBJCOPY variable definition.

gnu: icedtea6: patch ant shebang in unpack phase

* gnu/packages/java.scm (icedtea6)[arguments]: patch bootstrap ant in the
  `unpack' phase instead of `patch-paths'.

gnu: Add openblas.

* gnu/packages/maths.scm (openblas): New variable.

gnu: Add utf8proc.

* gnu/packages/textutils.scm (utf8proc): New variable.

store: Default to a non-empty list of substituters.

Fixes <http://bugs.gnu.org/20163>.
Reported by Mark H Weaver <mhw@netris.org>.

* guix/store.scm (%default-substitute-urls): New variable.
  (set-build-options): Change default value of #:substitute-urls to
  %DEFAULT-SUBSTITUTE-URLS.

gexp: Fix handling of nativeness in nested gexps.

* guix/gexp.scm (gexp-inputs): Remove 'references' parameter; add
  #:native? and honor it.
  [add-reference-inputs]: Distinguish between native gexp inputs, and
  non-native gexp inputs.  Honor 'native?' field of list inputs.
* tests/gexp.scm ("ungexp + ungexp-native, nested"): New test.

gexp: Ignore nested gexps in macro expansion.

Before that, the 'references' and 'natives' or the outer gexp in an
expression like #~#+#~#$coreutils would include those of the inner
gexp.

* guix/gexp.scm (gexp)[collect-escapes]: Ignore everything below
  'ungexp-native' or 'ungexp-native-splicing'.
  [collect-native-escapes]: Ignore everything below 'ungexp' or
  'ungexp-splicing'.

gexp: Allow <gexp-input> objects in #:allowed-references.

* guix/gexp.scm (lower-references): Add <gexp-input> case.
* tests/gexp.scm ("gexp->derivation #:allowed-references, specific
  output"): New test.