BUG: add proper error handling when using interp2d on regular grids

fixes #1889
BUG: fix test for interp2d
Fix documentation for cKDTree.sparse_distance_matrix
DOC: stats: remove duplicated names from the mstats module docstring
MAINT: linalg.orth memory efficiency
MAINT: stats: A bit of docstring and whitespace clean up.
BUG: sparse/superlu: fix || vs && mistake in L/U attributes + add test
MAINT: cluster: some clean up work

Some useless docs, comments and code in cluster.vq are removed.
Some errors in the docs of cluster.hierarchy.dendrogram are
fixed.
Merge pull request #3627 from WarrenWeckesser/stats-doc

MAINT: stats: A bit of clean up
Merge pull request #3625 from thouis/patch-1

Fix documentation for cKDTree.sparse_distance_matrix
Merge pull request #3635 from pv/splu-lu-bug

BUG: sparse/superlu: fix || vs && mistake in L/U attributes + add test
Fixed confusion between 'minimum' and 'minima' in docstring of optimize.basinhopping
Corrected doctest for "singular of 'minima' is 'minimum' issue"
TST: orth regression test will now fail instead of error under regression
TST: fix a number of test errors for ``test('full')`` with numpy master.
TST: ignore deprecation warnings for optimize.anneal
Merge branch 'pr/3616' into master.

Review at https://github.com/scipy/scipy/pull/3616
Merge pull request #3638 from chatcannon/basinhopping_doc

DOC: docstring of optimize.basinhopping confuses singular and plural of 'minimum'
Merge pull request #3636 from richardtsai/cluster_vq_cleanup

MAINT: cluster: some clean up
BUG: change ddof default to 1 in mstats.sem, consistent with stats.sem.

See discussion on https://github.com/scipy/scipy/pull/3458 for details.