[SSSD] [PATCH] Fix python HBAC bindings for python <= 2.4

[Jakub Hrozek]

Several parts of the HBAC python bindings did not work on old Python
versions, such as the one shipped in RHEL5.

The changes include:
 * a compatibility wrapper around python set object
 * PyModule_AddIntMacro compat macro
 * HbacRule.enabled is now a getsetter to avoid using T_BOOL which is
   not present in old Python versions
 * Py_ssize_t compat definition
 * Do not use PyUnicode_FromFormat
 * several function prototypes and structures used to have "char *"
   arguments where they have "const char *" in recent versions. This
   caused compilation warnings this patch mitigates by using the
   discard_const hack

It also plugs one memory leak - HbacRequest.rule_name wasn't freed in
HbacRequest destructor.