daemon: Fix 'HashSink::currentHash()'.

Before that, calls to 'HashSink::currentHash()' would eventually lead to
a segfault because the underlying gcrypt handle has been closed.  (Note
that this method is only used via 'importPaths' and 'exportPath', though.)

* nix/libutil/gcrypt-hash.hh (struct guix_hash_context): Add a
  constructor and a copy constructor; move out of 'extern "C"'.
* nix/libutil/gcrypt-hash.cc (guix_hash_final): Clear 'md_handle' upon
  exit.
* nix/sync-with-upstream (top_srcdir): Change hash.{cc,hh} to read
  'struct Ctx' instead of 'union Ctx'.

Merge branch 'master' into core-updates

daemon: Use 'int' instead of the internal 'gcry_md_algo_t' type.

Fixes compilation with the forthcoming libgcrypt 1.6.x.
Reported by Matthias Wachs <wachs@net.in.tum.de>
and NIIBE Yutaka <gniibe@fsij.org>.

* nix/libutil/gcrypt-hash.cc (guix_hash_init, guix_hash_final): Use
  'int' as the type of the 'algo' parameter.
* nix/libutil/gcrypt-hash.hh: Update declarations accordingly.

Merge branch 'master' into core-updates

Conflicts:
	build-aux/download.scm
	distro/packages/autotools.scm
	distro/packages/base.scm
	distro/packages/bootstrap.scm
	distro/packages/lsh.scm
	distro/packages/make-bootstrap.scm
	distro/packages/ncurses.scm
	distro/packages/perl.scm
	tests/derivations.scm
	tests/union.scm

Update license headers.

Change all license headers, except guix/build/* and ld-wrapper.scm, with
this code:

  (use-modules (guix build utils)
	       (srfi srfi-1))

  (fluid-set! %default-port-encoding "UTF-8")

  (substitute* (remove (lambda (f)
			 (or (string-contains f ".tar.")
			     (string-contains f ".git/")
			     (string-contains f ".so")
			     (string-suffix? ".o" f)
			     (string-suffix? ".a" f)
			     (string-suffix? ".go" f)
			     (string-suffix? ".pdf" f)
			     (string-suffix? ".png" f)
			     (string-suffix? ".info" f)
			     (equal? (basename f) "guix-daemon")
			     (equal? (basename f) "nix-setuid-helper")
			     (string-contains f "nix-upstream/")
			     (string-contains f "distro/packages/bootstrap/")))
		       (find-files "." "\\.[a-z]+$"))
    (("^([[:graph:]]+) This file is part of Guix." _ comment-start)
     (string-append comment-start " This file is part of GNU Guix."))
    (("^([[:graph:]]+) Guix --- Nix package management.*" _ comment-start)
     (string-append comment-start
		    " GNU Guix --- Functional package management for GNU\n"))
    (("^([[:graph:]]+) Guix is " _ comment-start)
     (string-append comment-start " GNU Guix is "))
    (("^([[:graph:]]+) along with Guix." _ comment-start)
     (string-append comment-start " along with GNU Guix."))
    (("^([[:graph:]]+) Copyright \\(C\\)" _ comment-start)
     (string-append comment-start " Copyright ©")))

Change headers using C-style comments manually.

Merge branch 'nix-integration'

Conflicts:
	tests/guix-package.sh

daemon: Fix typo in libgcrypt bindings.

* nix/libutil/md5.h (MD5_Final): Pass RESBUF as the first argument to
  `guix_hash_final'.
* nix/libutil/sha1.h (SHA1_Final): Likewise.
* nix/libutil/sha256.h (SHA256_Final): Likewise.

build: Include a copy of Nix's libstore and daemon; build it.

* configure.ac: Call `AC_USE_SYSTEM_EXTENSIONS', and
  `GUIX_SYSTEM_TYPE'.  Add `--with-store-dir' option, and substitute
  `storedir'.  Include `config-daemon.ac'.
* config-daemon.ac: New file.
* Makefile.am [BUILD_DAEMON]: Include `daemon.am'.
* daemon.am: New file.
* m4/guix.m4 (GUIX_SYSTEM_TYPE): New macro.

* nix/libutil/gcrypt-hash.cc, nix/libutil/gcrypt-hash.hh,
  nix/libutil/md5.h, nix/libutil/sha1.h, nix/libutil/sha256.h,
  nix/nix-daemon/guix-daemon.cc, nix/nix-daemon/shared.hh: New files.