ENH: signal: spectral: Add periodogram and welch functions
BUG: signal: spectral: fix various bugs in periodogram and welch.

1. various off by 1 issues in dealing with the output of fftpack.rfft.
2. the DC and nfft/2 points shouldn't be scaled by 2 for 'onesided'
3. error in computing frequency axis in 'onesided'

The output of welch exactly matches matplotlib.mlab.psd for both even
and odd length  one-sided spectra and even length two-sided spectra of
real data.  For odd length two-sided spectra of real data, welch matches
the spectrum but matplotlib.mlab.psd return an incorrect frequcny axis.
BUG: signal: spectral: Fix bug introduced in last commit

We want fftbins=True in signal.get_window.  matplotlib.mlab.psd
effectively uses fftbin=False since this option doesn't exist in numpy.
Swapped this in to do some testing.
ENH: signal: spectral: Support detrending in welch.
MAINT: signal:  update binary attrib on _spectral.c

This marking was lost when the file was renamed.
BUG: signal: welch: call detrend instead of doing it by hand.

To support detending via a polynomial, we could extend detrend.
TST: signal: add test for welch

Also, fix bug in welch.
TST: signal: add tests for periodogram
DOC: fix formatting of signal._peak_finding docs, add missing parameters.
add platform specific include path to search paths

the path can diverge on some platforms e.g. ubuntu 13.04 with python3.3
based on patch by Matthias Klose in ubuntu
add scipy/interpolate/interpnd.pyx.in to source tarball (#1780)
Merge pull request #380 from juliantaylor/dfsg-clean

BLD: add scipy/interpolate/interpnd.pyx.in to source tarball (#1780)
include swig files in source dist too
fix a couple of spelling errors
Merge pull request #379 from juliantaylor/multiarch-includes

add platform specific include path to search paths
BUG: signal: spectral: address review comments
DOC: Capitalize Mathieu and some other proper names
Merge pull request #383 from endolith/capitalize_names

DOC: Capitalize Mathieu and some other proper names
BUG: sparse.linalg: initialize variables correctly in init and dealloc
BUG: sparse.linalg: deallocate Python object correctly (fixes #1789)