gethostbyaddr().  (Plain gethostbyname() returns only the IP address.)
This moves the code shared by gethostbyaddr() and gethostbyname_ex()
to a subroutine.

Original patch by Dan Stromberg; some tweaks by GvR.

so that our #ifdef test has the wrong effect.  Substitute hardcoded
values for some important symbols (but not for the whole range -- some
are pretty obscure so it's not worth it).

comments.

called!

(1) Use PyErr_NewException("module.class", NULL, NULL) to create the
    exception object.

(2) Remove all calls to Py_FatalError(); instead, return or
    ignore the errors -- the import code now checks PyErr_Occurred()
    after calling a module's init function, so it's no longer a
    fatal error for the initialization to fail.

Also did some small cleanups, e.g. removed unnecessary test for
"already initialized" from initfpectl(), and unified
initposix()/initnt().

I haven't checked this very thoroughly, so while the changes are
pretty trivial -- beware of untested code!

exception -- return it as a tuple.  Seems useful in promiscuous mode.

Use PyArg_ParseTuple() where it makes sense.

Avoid core dumps in resizestring().