DOC: Add Notes section to chebwin docstring
ENH: expose control truncation of ndimage.gaussian_filter().

This change gives the user control over the size at which the Gaussian filter is truncated,
with default behavior to truncate at 4 standard deviations (the previous fixed value).
ENH: Pass extra keyword arguments to gaussian_laplace() and gaussian_gradient_magnitude() to gaussian_filter()

This change allows control over the truncation radius of the gaussian filter used in
gaussian_laplace() and gaussian_gradient_magnitude().
TST: ndimage: add more tests in test_gaussian_truncate()
DOC: use raw docstring so math doesn't need double backslashes
FIX: raise NotImplementedError, not NotImplemented

or else raising this error raises an error:

TypeError: 'NotImplementedType' object is not callable
Comment: NotImplemented is returned, while NotImplementedError is raised
FIX: raise NotImplementedError, not NotImplemented
Revert "BLD: special: fix build when system doesn't have isfinite macro"

This fix broke windows builds.

This reverts commit 091e6fc93d90a9c63ecdbab2bbbee1673902eb1f.
BUG: fix build on RH5.
MAINT: signal: Some clean up in _peak_finding.py:

* Fixed the description of the return value of argrelmin, argrelmax,
  argrelextrema and _boolrelextream.
* Fixed the example in the docstring of _boolrelextream.
* Added examples to the docstrings of argrelmin, argrelmax and
  argrelextrema.
* Added more tests for argrelmin and argrelmax.
* Removed some commented-out code and unused imports from test_peak_finding.py
  along with an unused variable (num_peaks) in _gen_gaussians().
* Removed an argument ('order=2') from the signature of
  TestArgrel.test_higher_order() in test_peak_finding.py.
* Removed unnecessary special check in argrelextrema that incorrectly
  returned a length 2 tuple when there were no relative extrema,
  regardless of the dimension of the input.  Fixes gh-2832.
* Several more minor tweaks.
Merge pull request #2833 from cournape/fix_windows_build

BUG: special: Fix windows build
Merge pull request #2836 from WarrenWeckesser/maint-peak-finding-gh-2382

BUG: signal: Some clean up in _peak_finding.py

    Fixed the description of the return value of argrelmin, argrelmax, argrelextrema and _boolrelextream.
    Fixed the example in the docstring of _boolrelextrema.
    Added examples to the docstrings of argrelmin, argrelmax and argrelextrema.
    Added more tests for argrelmin and argrelmax.
    Removed some commented-out code and unused imports from test_peak_finding.py along with an unused variable (num_peaks) in _gen_gaussians().
    Removed an argument ('order=2') from the signature of TestArgrel.test_higher_order() in test_peak_finding.py.
    Removed unnecessary special check in argrelextrema that incorrectly returned a length 2 tuple when there were no relative extrema, regardless of the dimension of the input. Fixes gh-2832.
    Several more minor tweaks.
Merge pull request #2828 from endolith/patch-2

BUG: NotImplementedError != NotImplemented
Merge pull request #2777 from endolith/chebwin_docstring

DOC: signal: add Notes section to chebwin docstring
Merge pull request #2767 from WarrenWeckesser/thouis-gaussian-filter-more-tests

ENH: ndimage: gaussian filter truncation