rpc: reproducible genprotocol output

If the same source gets built twice ('build same source on different
hosts at different times') the resulting files may differ.
Fix this by sorting the hash keys before usage.
Signed-off-by: NOlaf Hering <olaf@aepfle.de>

src/rpc/genprotocol.pl

@@ -104,7 +104,7 @@ while (<RPCGEN>) {
         if (keys %uses >= 1) {
             my $i = 1;
 
-            foreach (keys %uses) {
+            foreach (sort(keys %uses)) {
                 $i = $uses{$_};
                 unshift @function,
                 ("        char **objp_cpp$i = (char **) (void *) &$_;\n");