DEP: non-integer scalar python sequence repeat

This starts deprecation for code such as
np.float_(3.4) * [1, 2]
which should only work for integer objects. It may be possible
to just return NotImplemented since at least python sequences
implement their multiply themself through __index__.

Further action is only needed for PyArray_PyIntAsIntp, so this
is part of a larger deprecation now.

Closes gh-4036
DOC: Spelling correction for numpy.diag see also
Spelling: loose -> lose
spelling: AC -> AD in years

(could also use BCE and CE to be more politically correct)
Merge pull request #4046 from chatcannon/speling

Spelling & notation corrections
Merge pull request #4038 from seberg/issue-4036

DEP: non-integer scalar python sequence repeat