fix some warnings

njvm.c

@@ -31,7 +31,8 @@ void stackPush(unsigned int value){
     stack[current] = value;
     current++;
 }
-unsigned int stackPop(){
+
+unsigned int stackPop(void) {
     if (current < 1) {
         fprintf(stderr, "stack underflow\n");
         exit(EXIT_FAILURE);
@@ -39,11 +40,11 @@ unsigned int stackPop(){
     return --current;
 }
 
-void version() {
+void version(void) {
     printf("Ninja Virtual Machine version %i (compiled %s, %s)\n", 0, __DATE__, __TIME__);
 }
 
-void help() {
+void help(void) {
     printf("usage: ./njvm [option] [option] ...\n\t--version\tshow version and exit\n\t--help\t\tshow this help and exit\n");
 }
 
@@ -58,7 +59,8 @@ void useption(int argc, char *argv[]){
         }
     }
 }
-void execute(){
+
+void execute(void) {
     int i = 0;
     while (programmSpeicher[i] != 0) {