Fix compilation on Solaris
Fix bugs related to bottom kwarg in step histograms

Conflicts:

	lib/matplotlib/axes.py
	lib/matplotlib/tests/baseline_images/test_axes/hist_step.png
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
fixed an enconding bug when checking for gs version
add failing test: savefig(StringIO(), format="ps")
Updated the docs of pyplot.gca.
Consider ourselves interactive if sys.flags.interactive is set.
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)
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
overloaded `_make_twin_axes` on `LocateableAxesBase` so that twinx and
twiny will work.
Merge pull request #2472 from mdboom/twin-spines-on-top

Plots using twinx draw on top of figure frame