Trac #14993: update matplotlib to version 1.3.1

This version of matplotlib has new dependencies, so create new
packages for dateutil, pyparsing, six, and tornado: all
straightforward, no patching required.
Trac #14993: update dependencies for the dateutil package.
Trac 14993: remove extraneous backquote character in matplotlib/spkg-install
Initial additon of the pkgconf package
Initial additon of the pkgconfig Python package
Make pkgconf and pkgconfig standard packages
Do not use ln -sf
serialize python install to avoid race
Install pkgconfig first instead of last
license clarifications
Merge branch 'develop' into matplotlib
fix sagenb checksums.ini
remove obsolete patch
Merge branch 't/15742/pkgconfig' into t/14993/matplotlib_1_3_1
add pkg-config dependency to matplotlib
Trac #15742: Pkgconfig

Make pkg-config available to Sage

This ticket adds a C implementation of the pkg-config spec together with
a Python interface to Sage. This will be used in the future to make
linking to libraries easier.

Upstream tarballs:
*
http://rabbit.dereferenced.org/~nenolod/distfiles/pkgconf-0.9.4.tar.bz2
* https://pypi.python.org/packages/source/p/pkgconfig/pkgconfig-1.1.0.ta
r.gz

URL: http://trac.sagemath.org/15742
Reported by: vbraun
Ticket author(s): Volker Braun
Reviewer(s): François Bissey
Trac #14993: Upgrade matplotlib to 1.3.1

Matplotlib 1.3.1 was released.  Here is what is new:
http://matplotlib.org/1.3.1/users/whats_new.html#new-in-matplotlib-1-3

Of particular note is that pytz, dateutil, and pyparsing are no longer
included and need to be installed separately:
http://matplotlib.org/1.3.0/users/whats_new.html#new-setup-script

---------

Files to be added to the `upstream` directory:

- http://sage.math.washington.edu/home/palmieri/SPKG/matplotlib-1.3.1.ta
r.gz (not vanilla source, as explained in SPKG.txt: a lot of graphics
files have been removed)
- http://sage.math.washington.edu/home/palmieri/SPKG/dateutil-2.2.tar.gz
- http://sage.math.washington.edu/home/palmieri/SPKG/pyparsing-2.0.1.tar
.gz
- http://sage.math.washington.edu/home/palmieri/SPKG/six-1.4.1.tar.gz
-
http://sage.math.washington.edu/home/palmieri/SPKG/tornado-3.1.1.tar.gz

Regarding the dependency on #15510: that ticket provides a recent
version of `setuptools`. Without that, the matplotlib build will (on-
the-fly) download the deprecated Python package `distribute`. It seems
to work fine either way.

Regarding all of these new files in `upstream`: as noted, matplotlib now
no longer includes various dependencies. I thought it would be helpful
to include them as separate files, in case other packages need them:
then the dependencies in `build/deps` can be made precise and explicit.

Regarding the patch to `setupext.py`: I'm not sure I converted it
properly from the old version to the new one. It works on OS X 10.9, but
there might very well be a better way to do it.

URL: http://trac.sagemath.org/14993
Reported by: jason
Ticket author(s): John Palmieri
Reviewer(s): François Bissey