BUG: cluster.linkage array conversion to double dtype
BUG: sparse: fix operator overloading with custom types

See issue #3580.
ENH: sparse: inplace ops should fall back to x = x op y if not implemented
BUG: sparse: itruediv should be allowed on sparse matrix
Sort netcdf variables in a Python-3 compatible way

The previous implementation ran into issues with comparing different
types (tuples and bools).

Also simplified the sorting, since Python 2.3 support is no longer an
issue.
Add test for zero dimensional netCDF variables
Ensure isrec always returns a boolean
Placate irritating pep8 checker
Fix for #3596: Make fftconvolve threadsafe
Consolidate duplicated code in fftconvolve
Fix small typo in comment
Adds default params to pdfs of multivariate_norm

Adds default params to pdf and logpdf to match
`norm` and the documentation.
ENH: Added support for date attributes to io.arff.arffread

Requires numpy >= 1.7
Throw exception of date attribute contains time zone information

Updated unit tests
Skip datetime tests if numpy < 1.7.0
Skip setUp when numpy < 1.7.0
BUG: signal.welch: ensure floating point dtype regardless of input dtype

Fixes gh-3655.
BUG: interpolate/fitpack: arguments to fortran routines may not be aliased

Fixes gh-2911
Merge pull request #3667 from tshauck/multivariate-norm-docs

ENH: Adds default params to pdfs of multivariate_norm
Merge pull request #3657 from ewmoore/specint

BUG: signal.welch: ensure floating point dtype regardless of input dtype