ENH: disable OpenBLAS affinity settings

OpenBLAS starts as many threads as it can and assigns them to cpus
This includes the main thread Python is running in.
This means any threads or processes Python starts must all share this
cpu, nullifying any parallization efforts.
Luckily this behaviour can be disabled via an environment variable which
we need to set before loading dotblas which may be linked to OpenBLAS.
Libraries loading BLAS before numpy are stills screwed.
BUG: Fix memory leak.

Patch is from Julian Taylor. Closes #4652.
Merge pull request #4654 from charris/fix-memory-leak-gh-4652

BUG: Fix memory leak.
Merge pull request #4580 from juliantaylor/openblas-affinity

ENH: disable OpenBLAS affinity settings
MAINT: Refactor numpy/polynomial/_polybase.py

1) Clean up the code and move repeated snippet to a method.
2) Remove use of has_sametype, has_samewindow, has_samedomain. I would
   like to deprecate those methods.
3) Fix error in __truediv__, and make it only allow non-boolean numbers
   for the denominator.

Closes #4631.
BUG: Fix __truediv__ bug in polytemplate.py file.

The use of polytemplate is deprecated, this fix is only for a backport
if needed.
TST: Add tests for the polynomial classes true division.
DOC/FIX: Fix error in documentation

Remove misleading note about equivalency betwen column_stack and
np.vstack(tup).T.

Fixes #3488
BUG: Fix use of setuptools.command.install._install.

This private variable has disappeared in later versions of setuptools.
In older versions of setuptools it is the same as
distutils.command.install.install, so use that instead.

Closes #4664.
Merge pull request #4667 from charris/fix-numpy-distutils

BUG: Fix use of setuptools.command.install._install.
Merge pull request #4633 from charris/fix-polynomial-true-division

Fix polynomial true division
Merge pull request #4666 from ElDeveloper/issue-3488

DOC/FIX: Fix error in documentation