fix mkpty function declarations

cli/main.c

@@ -1,6 +1,7 @@
-#include "mkpty.h"
-#include "sys/types.h"
+#include <stdio.h>
+#include <stdlib.h>
 
+#include "mkpty.h"
 
 // struct d_window {
 //   int ptmx; // fd
@@ -16,9 +17,14 @@ int main(int argc, char **argv) {
   pid_t pid;
   switch (pid = forkmkpty()) {
   case -1:
+    perror("forkmkpty");
     break;
   case 0:
+    printf("fork: children\n");
+    break;
   default:
+    printf("fork: parent\n");
     break;
   }
+  return EXIT_SUCCESS;
 }