32-bit platforms only support a slice offset start of 24 bit max due to the
limited size of the mp_obj_array_t.free member. Similarly on 64-bit
platforms the limit is 56 bits.
This commit adds an OverflowError if the user attempts to slice a
memoryview beyond this limit.
Signed-off-by: Damien George <damien@micropython.org>
Andrew Leech