guix gc: Add '--free-space'.

* guix/scripts/gc.scm (show-help, %options): Add '--free-space'.
(guix-gc)[ensure-free-space]: New procedure.
Handle '--free-space'.

syscalls: Add 'statfs'.

* guix/build/syscalls.scm (<file-system>): New record type.
(fsword): New macro.
(%statfs): New C struct.
(statfs): New procedure.

syscalls: 'define-c-struct' computes the struct size.

* guix/build/syscalls.scm (struct-alignment, struct-size): New macros.
(define-c-struct): Add 'size' parameter and honor it.
(sockaddr-in, sockaddr-in6, ifaddrs, winsize): Adjust accordingly.
(%struct-ifaddrs-type, %sizeof-ifaddrs, winsize-struct): Remove.
(terminal-window-size): Use 'make-bytevector' instead of 'make-c-struct'.

syscalls: Second argument of packed-struct read is now optional.

* guix/build/syscalls.scm (define-c-struct)[read]: OFFSET defaults to 0.
(unfold-interface-list): Remove second argument to 'read-ifaddrs'.
(terminal-window-size): Remove second argument to 'read-winsize'.

syscalls: Move code around [NFC].

* guix/build/syscalls.scm: Move packed structure handling to the top.

Add "TasksMax=1024" in 'guix-daemon.service'.

Suggested by Joram Schrijver <i+guix-devel@joram.io>.

* etc/guix-daemon.service.in (TasksMax): New value.

gnu: python2-pysnptools: Update to 0.3.9.

* gnu/packages/python.scm (python2-pysnptools): Update to 0.3.9.
[propagated-inputs]: Add python2-pytz. Move python2-pandas ...
[inputs]: ... to here. Add python2-dateutil-2, python2-six.

gnu: python-terminado: Update to 0.6.

* gnu/packages/python.scm (python-terminado): Update to 0.6.
[inputs]: Remove python-setuptools. Move python-nose ...
[native-inputs]: ... to here.
[properties]: Define python2-variant.
(python2-terminado): Build with 'strip-python2-variant'.
[native-inputs]: Add python2-setuptools.

gnu: python-singledispatch: Rearrange inputs.

* gnu/packages/python.scm (python-singledispatch)[propagated-inputs]:
Move python-six ...
[inputs]: ... to here.

gnu: python-tornado: Rearrange inputs.

* gnu/packages/python.scm (python-tornado)[properties]: Define
python2-variant.
[inputs]: Remove python-certifi, move python-backports-abc here from
native-inputs.
[native-inputs]: Remove python-setuptools.
(python2-tornado): Build with 'strip-python2-variant'.
[native-inputs]: Add python2-setuptools.

gnu: python-seaborn: Update to 0.7.0.

* gnu/packages/python.scm (python-seaborn): Update to 0.7.0.
[native-inputs]: Remove python-setuptools.
(python2-seaborn): Build with 'strip-python2-variant'.
[propagated-inputs]: Add python2-pytz.
[native-inputs]: Add python2-setuptools.

gnu: python-pandas: Rearrange inputs.

* gnu/packages/python.scm (python-pandas)[propagated-inputs]: Move
python-pytz, python-dateutil-2 ...
[inputs]: ... to here.

gnu: xfce: Add ristretto.

* gnu/packages/xfce.scm (xfce)[propagated-inputs]: Add ristretto.

gnu: Add ristretto.

* gnu/packages/xfce.scm (ristretto): Add variable.

gnu: ncmpcpp: Update to 0.7.4.

* gnu/packages/mpd.scm (ncmpcpp): Update to 0.7.4.

gnu: borg: Update to 1.0.2.

* gnu/packages/backup.scm (borg): Update to 1.0.2.

gnu: haunt: Update to 0.2.

* gnu/packages/guile.scm (haunt): Update to 0.2.
[native-inputs]: Add pkg-config and texinfo.
[propagated-inputs]: Add guile-reader.

gnu: guile-minikanren: Remove extra .scm on files.

* gnu/packages/guile.scm (guile-minikanren): Remove extra .scm appended
to files.

gnu: guix: Update development snapshot.

* gnu/packages/package-management.scm (guix-devel): Update to 80627f5.

gnu: openldap: Update to 2.4.44 [fixes CVE-2015-6908].

* gnu/packages/openldap.scm (openldap)[replacement]: New field.
(openldap-2.4.44): New variable.