Switch to PyMODINIT_FUNC annotation

Instead of doing some 'extern ...' declaration magic to force
proper PyInit_libvirtmod*() symbol exposure in resulting .so we
can use what Python already offers - PyMODINIT_FUNC macro and
call it a day.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

libvirt-qemu-override.c

@@ -25,12 +25,6 @@
 # include <fcntl.h>
 #endif
 
-#ifndef __CYGWIN__
-extern PyObject *PyInit_libvirtmod_qemu(void);
-#else
-extern PyObject *PyInit_cygvirtmod_qemu(void);
-#endif
-
 #if 0
 # define DEBUG_ERROR 1
 #endif
@@ -478,7 +472,7 @@ static struct PyModuleDef moduledef = {
     NULL
 };
 
-PyObject *
+PyMODINIT_FUNC
 #ifndef __CYGWIN__
 PyInit_libvirtmod_qemu
 #else