bugfix: when syncing only try every second input value

lib/sync_decim_impl.cc

@@ -127,7 +127,7 @@ namespace gr {
             int skip_is_better_counter=0;
             if (noutput_items>8)//TODO: what if there are never more than 9 outputs requested
             {
-              for (int i = 0; i < noutput_items; i++) {
+              for (int i = 0; i < noutput_items; i+=2) {
                 if(i==0){
                   out_skip=last_input-in[DECIM*i];}
                   else{