Disallowing timedelta64+float promotion (to timedelta64) in all cases
(previously it was assymetric and "half allowed") meant that isclose,
allclose, np.ma.allclose, and assert_arrays_almost_equal (which uses
isclose), would stop work for timedelta64. Hardcoding that timedelta64
is passed on unmodified retains the old behaviour.

It may make sense to deprecate or change this behaviour in the future,
but for the 1.20 release, the behaviour should be as much unmodified
as possible.

Closes gh-18286

Space before colon, or missing colon in see-also,
typo in parameter names, casing in See Also.

... or when the input isn't/cannot be a set.  I left a few usages, e.g.
in random sampling, where "set" is reasonable as informal description of
an array as the order doesn't matter; however, for e.g. np.gradient the
order of the returned list is clearly important, so "set" is wrong.

Also some other minor doc edits noticed during the grepping: using
`shape` instead of `form` in `cov` is consistent with most other places;
the wording in `Polynomial.trim` now matches other methods on the same
class.

Closes #17944

The `__new__` method of `MaskedArray` has the parameter `**options`,
but it is not used.  This means a mistyped parameter is silently ignored,
e.g. if I mistype the `mask` parameter like this, I don't get an error:

    In [2]: m = np.ma.MaskedArray([1, 2, 3], maks=[0, 1, 0])

    In [3]: m
    Out[3]:
    masked_array(data=[1, 2, 3],
                 mask=False,
           fill_value=999999)

In this PR, I simply remove `**options` from the signature of
`MaskedArray.__new__`.  This affected one test.  That test was passing the
argument `shape=(0, 1, 2)` to the constructor of a subclass of `MaskedArray`,
but since any unknown keywords were silently ignored, that use of `shape` had
no effect.  I replaced it with the positional argument `[[[]], [[]]]`, which
I believe has the effect that was originally intended with the use of the
`shape` argument.

Fix broken links in see also section of some ma functions.

* fix np.ma.core.doc_note