Changing to dtype of a different size now requires contiguity of only the last axis
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Previously, viewing an array with a dtype of a different itemsize required that
the entire array be C-contiguous. This limitation would unnecessarily force the
user to make contiguous copies of non-contiguous arrays before being able to
change the dtype.

This change affects not only ``ndarray.view``, but other construction
mechanisms, including the discouraged direct assignment to ``ndarray.dtype``.

This change expires the deprecation regarding the viewing of F-contiguous
arrays, described elsewhere in the release notes.
