add new PR_SET_THP_DISABLE and PR_GET_THP_DISABLE prctl flags

they can be used to set or query if transparent huge pages are disabled.
introduced in linux 3.15 commit a0715cc22601e8830ace98366c0c2bd8da52af52

include/sys/prctl.h

@@ -92,6 +92,9 @@ extern "C" {
 
 #define PR_GET_TID_ADDRESS      40
 
+#define PR_SET_THP_DISABLE      41
+#define PR_GET_THP_DISABLE      42
+
 int prctl (int, ...);
 
 #ifdef __cplusplus