This new version of the patch modifies getargs.c and use
PyObject_GetBuffer and PyBuffer_Release in place of the raw bf_getbuffer
and bf_releasebuffer.
Also make sure that each GetBuffer is matched with a ReleaseBuffer
(except for s* and w*, where the calling code is responsible for this)

This seems to correct most of the refleaks mentioned above, except:

- test_unittest leaks 120 refs because the 'audioop' module is
re-imported many times. See issue3667, or the test case should be dropped.

- test_binascii leaks one time because of issue3668.