Fix build errors on Ubuntu 12.04.

From: Vinson Lee <[email protected]>

CC syscalls/prctl.o
syscalls/prctl.c:33:13: error: ‘PR_SET_CHILD_SUBREAPER’ undeclared here (not in a function) syscalls/prctl.c:33:37: error: ‘PR_GET_CHILD_SUBREAPER’ undeclared here (not in a function) syscalls/prctl.c:34:23: error: ‘PR_GET_TID_ADDRESS’ undeclared here (not in a function)

---
 include/compat.h |    3 +++
 1 file changed, 3 insertions(+)

index 51f0936..30edc81 100644
@@ -257,6 +257,9 @@ enum {
 
 #ifndef PR_SET_MM
 #define PR_SET_MM               35
+#endif
+
+#ifndef PR_SET_CHILD_SUBREAPER
 #define PR_SET_CHILD_SUBREAPER  36
 #define PR_GET_CHILD_SUBREAPER  37
 #define PR_SET_NO_NEW_PRIVS     38

1.7.9.5