Fix compilation on Solaris
Merge branch 'v1.3.x'

* v1.3.x:
  Document API change in hist
patch to fix issue #2473.

The change to the agg propagate to how `imsave` works so one test had
to be changed to account for the fact that pixels with alpha=0 are now
set to (1, 1, 1, 0) instead of (0, 0, 0, 0).
added class variable `_fill_color` to RendererAgg to hold the
color to use in `clear` calls to the render_base.

Changed all uses of `clear((...))` -> `clear(_fil_color)`.
changes to c++ because gcc 4.8 seems to allow things the compiler
on travis will not.
Fix #2472: Draw the spines on top of twin axes
ENH better error message when wrong cmap name.

Now prints all possible choices
fixed an enconding bug when checking for gs version
add failing test: savefig(StringIO(), format="ps")
Updated the docs of pyplot.gca.
Merge pull request #2502 from pelson/gca_doc

Updated the docs of pyplot.gca.
minor docstring fix in dates.py
tiny correction of matplotlibrc.template

remove quotes around text.hinting default value (i.e. auto)
Merge pull request #2485 from NelleV/error_message

ENH better error message when wrong cmap name.
add new ps backend test file in `__init__.py`
Fix writing to all manner of StringIO-like objects in PS backend.
pep8
- pep8
 - removed mutable default values
 - foo == None -> foo is None
Merge pull request #2472 from mdboom/twin-spines-on-top

Plots using twinx draw on top of figure frame
Merge pull request #2512 from mdboom/ps_StringIO

Fix saving to in-memory file-like objects in Postscript backend