on_exit replaced with in_exit2

Hey!
hey !
on_exit is in conflict because it's already defined in stdlib.h
(i got compile error)
Compile err:
cc -Wall    2048.c   -o 2048
2048.c:78:6: error: conflicting types for ‘on_exit’
 void on_exit() {
      ^
In file included from 2048.c:10:0:
/usr/include/stdlib.h:535:12: note: previous declaration of ‘on_exit’ was here
 extern int on_exit (void (*__func) (int __status, void *__arg), void *__arg)
            ^
<builtin>: recipe for target '2048' failed
make: *** [2048] Error 1

Please review!

thanks