[ENH] Support F-contiguous `memoryview`s in `cast`

[jakirkham]

Currently memoryview.cast requires C-contiguous data when going from N-D to 1-D. As a result F-contiguous data is not supported. Please see example below:

>>> mv.c_contiguous
False
>>> mv.f_contiguous
True
>>> mv.cast("B")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: memoryview: casts are restricted to C-contiguous views

However as F-contiguous data is still contiguous and can be viewed in 1-D, it seems possible to support this type of data as well. PickleBuffer's raw method does appear to support both C & F contiguous data. Building off the example above:

>>> from pickle import PickleBuffer
>>> pb = PickleBuffer(mv)
>>> pb.raw()
<memory at 0x1105cec70>

This would be useful when interacting with other libraries that work with this kind of data. That said, don't know if there is other context behind the C-contiguous constraint that I may be missing here.

[corona10]

I am working on this issue.