Add a local declaration of the internal su_random64 function from
sofia-sip, so that it can be called with compilers which do not
support implicit function declarations.

Submitted upstream: <https://gitlab.gnome.org/GNOME/calls/-/merge_requests/658>

diff --git a/calls-v44_alpha.1/plugins/provider/tests/test-sip.c b/calls-v44_alpha.1/plugins/provider/tests/test-sip.c
index d9c013fac30854c0..00fba3106aeec194 100644
--- a/calls-v44_alpha.1/plugins/provider/tests/test-sip.c
+++ b/calls-v44_alpha.1/plugins/provider/tests/test-sip.c
@@ -21,6 +21,8 @@
 #include <sofia-sip/su_uniqueid.h>
 #include <libpeas/peas.h>
 
+#include <stdint.h>
+
 typedef struct {
   CallsSipProvider *provider;
   CallsSipOrigin   *origin_alice;
@@ -430,6 +432,7 @@ main (int   argc,
 
   gst_init (NULL, NULL);
   /* this is a workaround for an issue with sofia: https://github.com/freeswitch/sofia-sip/issues/58 */
+  extern uint64_t su_random64 (void);
   su_random64 ();
 
   g_test_add ("/Calls/SIP/provider_object", SipFixture, NULL,