Add support for using openblas for the _dotblas function.
BLD: Update with information about openblas.
DOC: hfft/ihfft description conflicts with itself

Says Hermite spectrum when it means signal
DOC: Add examples, copy some text from rfft functions to clarify inputs and outputs
DOC: add note clarifying why ifftshift is needed
Small correction in the docstring of polyfit. As mentionned in Issue 3640, the notes were wrong in the order of the index for p.
Merge pull request #3653 from larsmans/c-fixes

FIX: call through wrong function pointer type + minor stuff
BUG: Set __hash__ = None for non-hashable classes.

Because neither poly1d nor the Polynomial package polynomial classes are
immutable, hence not reliably hashable, they should signal that by
setting __hash__ = None. This also fixes the warning

Overriding __eq__ blocks inheritance of __hash__ in 3.x

that is given when the command `python2.7 -3 -c"import numpy"` is run.
ENH: Avoiding conversion of integer to NumPy Scalar.
There is a bottleneck in scalar operations, when trying to extract the
underlying C value from a Python integer/float. I have avoid conversion
for know integer type but extracting its value.
Extracting longlong value without converting it to NyType
Moved int test cases to pr#3592
Added PyInt_CheckExact for python < 3 and error check for PyLong_AsLong
Replaced PyInt_As_Long with PyInt_AsLong and  errorchecking
Merge pull request #3651 from MatthieuDartiailh/polyfit_doc

Small correction in the docstring of polyfit.
DOC: change "Hermite" to "Hermitian", "though" to "although"
DOC: Remove parentheses around axis
FIX: unchecked mallocs and Python operations

Rewrote _tmp_string_t handling in buffer.c to use the fact that
realloc(NULL, n) is equivalent to malloc(n). There are still some
unchecked cases in this file.

Also changed some arguments to const and removed casts on malloc
return values; malloc returns void*, which is converted to any
other pointer automatically. Casting the return value of malloc
is more likely to hide bugs than to fix anything.
MAINT: remove unused goto label and useless casts
FIX: some more casts in ufunc_object

Introduced a helper function to get rid of repetitive code.
FIX don't explicitly cast void* when final type is known