build: Use Gnulib's 'git-version-gen'.

* Makefile.am (EXTRA_DIST, BUILT_SOURCES): Add $(top_srcdir)/.version.
($(top_srcdir)/.version, gen-tarball-version): New targets.
(dist-hook): Depend on 'gen-tarball-version'.
(.PHONY): Add 'gen-tarball-version'.
* build-aux/git-version-gen: New file, from Gnulib v0.1-1312-ga87d5e5c6.
* configure.ac: Use it in 'AC_INIT'.  Use 'https' for the URL.

build: Remove 'sync-descriptions' target.

This target predates 'guix lint'.  Nowadays it makes little sense to run
it upon 'make dist'.

* Makefile.am (sync-descriptions): Remove.
(dist-hook, .PHONY): Remove reference to 'sync-descriptions'.

dir-locals.el: Add 'modify-phases' keywords.

* .dir-locals.el: Add indentation rules for 'replace', 'add-before' and
'add-after'.

etc: indent-code.el: Define source tree by "indent-code.el".

* etc/indent-code.el.in: Set default directory by "indent-code.el"
itself, otherwise it works only when called from the top directory of
the guix source tree.

doc: Add references to Emacs-Guix manual.

* doc/htmlxref.cnf: Add links to the real manual.
* doc/contributing.texi (Formatting Code): Add reference to it.
* doc/guix.texi (Package Management): Likewise.

gnu: qca: Update to 2.1.3.

* gnu/packages/kde.scm (qca): Update to 2.1.3.
[home-page]: Use new home-page.

store: Use 'write-bytevector' instead of hand-coded equivalent.

* guix/store.scm (process-stderr): Use 'write-bytevector' in the
%STDERR-READ case.

store: Add store path computation procedures.

* guix/derivations.scm (compressed-hash, store-path)
(output-path, fixed-output-path): Move to...
* guix/store.scm: ... here.

gnu: fish-guix: Adjust the home-page.

* gnu/packages/shells.scm (fish-guix)[home-page]: Use the correct website.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu: Add gcc-toolchain@7.

* gnu/packages/commencement.scm (gcc-toolchain-7): New variable.

tests: Use 'fold-module-public-variables' for discovery.

* gnu/tests.scm (fold-system-tests): Write in terms of
'fold-module-public-variables'.

nls: Mark (guix discovery) as translatable.

This is a followup to cd903ef7871170d3c4eced45418459d293ef48a7.

* po/guix/POTFILES.in: Add 'guix/discovery.scm'.

gnu: neovim: Update to 0.2.0.

* gnu/packages/vim.scm (neovim): Update to 0.2.0.

gnu: lua5.2-libmpack: Fix make flags.

This is a follow-up to commit. b5236121065abe32a88f8f0644ceb505f5cf1d18.

* gnu/packages/serialization.scm (lua5.2-libmpack)[arguments]: Adjust make
flags.

gnu: lua-libmpack: Update to new upstream source.

Inheriting the source from libmpack no longer works, because upstream has
moved the Lua bindings to a separate repository.

This is a follow-up to commit b5236121065abe32a88f8f0644ceb505f5cf1d18.

* gnu/packages/serialization.scm (lua-libmpack)[source]: Use new upstream
source.
[arguments]: Adjust make flags and build phases.
[native-inputs]: Add package sources of libmpack.
[home-page]: Use new home page URL.

gnu: llvm-3.5: Fix build of clang-3.5.

* gnu/packages/patches/llvm-3.5-fix-clang-build-with-gcc5.patch: New file
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/llvm.scm (llvm-3.5)[source]: Add patch.

gnu: guile-bytestructures: Install sld files.

* gnu/packages/guile.scm (guile-bytestructures): Build and install sld
  files in r7 repository.

It fixes this kind of errors while using guile-bytestructures:

ice-9/psyntax.scm:3245:33: ice-9/psyntax.scm:3245:33: Syntax error:
/gnu/store/ny9mp091yw51ylv1q59z25z5vdw8bi56-profile/share/guile/site/2.2/bytestructures/guile/base.scm:8:19: include-from-path: file not found in path in subform "bytestructures/r7/base.exports.sld" of (include-from-path "bytestructures/r7/base.exports.sld")

gnu: man-pages: Update to 4.11.

* gnu/packages/man.scm (man-pages): Update to 4.11.

environment: Correct typo.

* guix/scripts/environment.scm (create-environment): Fix typo.

gnu: capnproto: Update to 0.6.0.

* gnu/packages/serialization.scm (capnproto): Update to 0.6.0.