Truncate the buffer size to PY_SSIZE_T_MAX.

Use Py_off_t type (64 bits) instead of off_t (32 bits).

Instead, the re module's standard caching does its work.

(thanks "make smelly")

tests from the setUp() routine.
This fixes a refleak in test_socket on some machines.

 * Call directly the right find/rfind method: allow inlining functions
 * Remove Py_LOCAL_CALLBACK (added for any_find_slice)

Thanks to Konrad Schöbel and Jasper Schulz for helping with the mass-editing.