MAINT: minor performance improvement

Merge two loops and move invariant of switch case out of inner loop.
Improves performance by 5% - 10% depending on the order.
MAINT: tell compiler that edge interpolation is less likely

This should be true for most cases where performance is relevant.
Improves performance by about 5% on images > (500, 500) with order three.
MAINT: add map_coordinate tests with non-continous arrays
ENH: stats: Some enhancements to the chisquare functions:

* Add the `axis` argument to stats.chisquare and stats.mstats.chisquare.
* Add the `ddof` argument to stats.mstats.chisquare.

Closes gh-2108 (trac #1583).
Merge pull request #503 from juliantaylor/ni_interpolation-performance

ENH: Ni interpolation performance improvements.
Modified the interpretation of the axis argument.

It is now the axis of the array resulting from broadcasting f_obs
and f_exp.

Also simplified the code a bit.
Update the docstring for mstats.chisquare, and change the casting of ddof in mstats.chisquare so the p value data type is correct when axis=None is used.
Merge pull request #2475 from pv/special-orthopoly

BUG: special: fix up a number of corner cases in orthogonal polynomials
MAINT: allow computation of variance in (a.o.?) non-central t-distribution.

Closes gh-2401.
ENH: Added bool_ops.h file which wraps npy_bool data to handle bool operations.
MAINT: stats: Improve chisquare docstrings, and add tests that compare stats.mstats.chisquare to stats.chisquare.
ENH: numpy.i & sparsetools.i interface files now include the bool_ops.h file to handle the npy_bool dtype.
ENH: Regenerated *.py and *.cxx files with SWIG
TST: Added tests for .toarray() & .todense() methods for dtype=bool spmatrices.
Merge pull request #2480 from WarrenWeckesser/stats-chisquare

ENH: stats: Some enhancements to the chisquare functions:
BUG: accept scalar mysize argument in signal.wiener

This makes it consistent with the documentation.
MAINT: fix non-integer usage in scipy.spatial.
MAINT: signal: clean up argument check in medfilt, medfilt2d, wiener
MAINT: fix non-integer usage in cluster and sparse.
MAINT: fix non-integer usage in io, interpolate and optimize.