graphics/gphoto2: fix the port's build against modern Clang 15

Cast `unsigned int' type properly when using it as a thread id.

Reported by:	pkg-fallout

graphics/gphoto2/files/patch-gphoto2_main.c

@@ -0,0 +1,19 @@
+--- gphoto2/main.c.orig	2020-07-02 06:39:33 UTC
++++ gphoto2/main.c
+@@ -1211,14 +1211,14 @@ start_timeout_func (Camera *camera, unsigned int timeo
+
+ 	pthread_create (&tid, NULL, thread_func, td);
+
+-	return (tid);
++	return (intptr_t)tid;
+ }
+
+ static void
+ stop_timeout_func (Camera __unused__ *camera, unsigned int id,
+ 		   void __unused__ *data)
+ {
+-	pthread_t tid = id;
++	pthread_t tid = (pthread_t)(intptr_t)id;
+
+ 	pthread_cancel (tid);
+ 	pthread_join (tid, NULL);