Implement (exit FIXNUM)

Add systemcall exit to the runtime environment.

source/primitives/system.c

@@ -22,6 +22,13 @@
 struct org_cherry_value*
 org_cherry_system_exit(struct org_cherry_environment* env, struct org_cherry_value* args)
 {
+	if(IS_NULL(args))
+		exit(EXIT_SUCCESS);
+	else if(IS_FIXNUM(HEAD(args)))
+		exit(HEAD(args)->fixnum_value);
+	else
+		org_cherry_env_raise(env, org_cherry_string("Exit is expecting a fixnum for the first argument"));
+
 	return org_cherry_false;
 }