I do not have the knowledge needed to review the code, but I took a brief look. The three doc patches need a verb to be proper English. "Samples truncated in case of overflow." should be "Samples are truncated in case of overflow." in both places. I think "Samples wrapped around in case of overflow." could be rewritten as "Samples wrap around in case of overflow.", though adding 'are' works too.

In the C code comment:

     /* Passing a short** for an 's' argument is correct only
        if the string contents is aligned for interpretation
        as short[]. Due to the definition of PyBytesObject,
-       this is currently (Python 2.6) the case. */
+       this is currently (Python 2.6) the case.
+       XXX: It's not true for memoryview. */

Is whatever the case in 2.6 only (if so, drop obsolete) or since 2.6. If the latter, I would rewrite as "this is the case since Python 2.6.".
The addition is not clear to me. Are you implying that something should be made true for memory view (in a future patch)?