Reviewed on IRC by Georg Brandl, with assistance by Benjamin Peterson.

Fix problems with memoryview object.  There is still more to do to finish PEP 3118.  The memory-view object needs to be fleshed out and the struct module needs to be modified.

Change PyBuffer to Py_buffer to be consistent with other non-object structures like Py_complex.  Add some more functionality to the memoryview object.