[USER] Exit and wait syscalls

libc/syscall_num.h

@@ -3,4 +3,6 @@
 #define SYS_WRITE 0x001
 #define SYS_BRK   0x002
 #define SYS_FORK  0x003
+#define SYS_EXIT  0x004
+#define SYS_WAIT  0x005
 #define SYS_DEBUG 0x3FF

libc/thread.c

@@ -42,3 +42,15 @@ SYSCALL_DEF(gettid)
   SYSCALL_INIT();
   return 0;
 }
+
+SYSCALL_DEF(exit_group)
+{
+  SYSCALL_INIT(int, result);
+  return kernel_syscall(SYS_EXIT, result);
+}
+
+SYSCALL_DEF(wait4)
+{
+  SYSCALL_INIT(int, pid, int *, result, int, options, void *, rusage);
+  return kernel_syscall(SYS_WAIT, result);
+}