MAINT: remove unused simple_capsule_dtor() from npy_3kcompat.h

This removes a lot of build warnings when including this file.
MAINT: remove unused variables from einsum.c.src and loops.c.src

Fixes some build warnings.
MAINT: fix build warnings for umath_linalg

The removal of CFLOAT for eig/eigvals is related to a bug, see c355550dd80.
Can be put back once that issue is fixed.
MAINT: fix build warnings in test_rational.c.src
MAINT: silence some build warnings due to missing NO_IMPORT_ARRAY
ENH: reduce overhead of probs check of choice

Use kahan_sum as multinomial does.
Closes gh-4188
MAINT: regenerate with cython 0.20 and fix a warning it emits

Fixed warning is "Non-trivial type declarators in shared declaration".
Merge pull request #4212 from rgommers/buildwarnings

Fix some build warnings
BUG: properly handle references of objects in new np.where

Objects must go over the objects copyswap function and GIL must be taken
before dereferences for correct reference counting.
DOC: add versionadded:: 1.8.0 to ufunc.at docstring
MAINT: fix some f2py related build warnings.
Merge pull request #4221 from rgommers/fix-f2py-warning

MAINT: fix some f2py related build warnings.
Merge pull request #4220 from juliantaylor/ufunc-at-ver

DOC: add versionadded:: 1.8.0 to ufunc.at docstring
Merge pull request #4213 from juliantaylor/choice-improv

improve random.choice performance and regen with cython 0.20
BUG: min_scalar_type_num: special float values can be represented in half

E.g. pandas sometime uses float('NaN') which would otherwise convert to
float64 where not required. The new np.where which uses
PyArray_ResultType is a case where the conversion is unnecessary.
DOC: document special float scalar casting change in release notes
BLD: Fix ANSI C syntax error

Fixes msvc9/10 error C2143: syntax error : missing ';' before 'type'
TST: fail on declaration-after-statement in travis test

required for windows compilers
TST: test non integer item does not return array

from gh-4223 in the 1.8 branch
Merge pull request #4215 from juliantaylor/where-obj-fix

BUG: fix reference count, thread safety and dtypes of np.where