Attached is a patch which adds POSIX capabilities support.  The following API functions are supported:

  * cap_clear
  * cap_copy_ext
  * cap_dup
  * cap_from_text
  * cap_get_flag
  * cap_get_proc
  * cap_init
  * cap_set_flag
  * cap_set_proc
  * cap_size
  * cap_to_text

The following API function is supported, but is broken with certain versions of libcap (I am running debian testing's libcap1, version 1.10-14, which has an issue;  I have reported this upstream):
  * cap_copy_int

The following API functions are in there as stubs, but currently are not compiled.  I need access to a machine to test these.  I will probably add autoconf tests for availability of these functions in due course:
  * cap_get_fd
  * cap_get_file
  * cap_set_fd
  * cap_set_file

The patch includes diffs to configure.  My autoconf is however at a different revision to that used on the python trunk.  You may want to re-autoconf configure.in.

I've added a few API tests to test_posix.py.