3.1: wrote simple nice() that returns 0

kernel/proc.c

@@ -819,3 +819,11 @@ void priodump(void){
     printf("\n");
   }
 }
+
+// Changes the priority of the process that has
+// a given pid to the value given, returns 1 if
+// the provided pid is valid, 0 otherwise
+int
+nice(int pid, int priority) {
+  return 0;
+}