ENH: interpolate: add the rescale argument to griddata and NearestNDInterpolator

When it was added to the linear and cubic nd interpolators, the
nearest-neighbor one and griddata() were missed.

Also, refactor NDInterpolatorBase to avoid some work that is unnecessary
in the nearest neighbor interpolator.
quick hack for fast CSC hstacking
ENH: adding fast-path for compressed hstack/vstack
using @pv's suggestion for more speed
adding fast-path checks to bmat
bmat case bug fixes
removing special cases for vstack/hstack

The performance gain isn't that significant (vs the bmat fast-path
detection)
BUG: sparse/bmat: use a safer csr/csc check

Also make the `axis` argument less confusing to read.
Merge pull request #3057 from perimosocordiae/patch-1

ENH: sparse: fast paths for hstack/vstack with csc/csr matrices

Roughly 5-10x speed-up for vstacking CSR and hstacking CSC format matrices.
Merge pull request #2979 from pv/rescale-griddata

ENH: interpolate: add the rescale argument to griddata and NearestNDInterpolator
Fix #3059, wrong dtype for sliced sparse matrices
PEP8: Fix recently introuced pep8 violations
Test dtype preservation in sparse matrix slicing
Addition to issue #3059
added return doc-string
pep8 clean up
Merge pull request #3060 from polyatail/master

BUG: sparse: fix wrong dtype for sliced sparse matrices
BUG: fix non normalized vectors in gen. eig solver

The eigenvectors returned by the generalized eigenvalue solver were not
normalized. This seems to be an error in the lapack function. This
commit adds a fix for scipy and a unit-test
TST Use same C runtime library as Python executable
Merge pull request #3065 from cgohlke/patch-1

TST: integrate: Use same C runtime library as Python executable
Merge pull request #3055 from kain88-de/fix_gen_eig_solver

BUG: linalg: fix non normalized vectors in gen. eig solver