add PR_*_FP_MODE prctl options

new in linux v4.0, commit 9791554b45a2acc28247f66a5fd5bbc212a6b8c8
used to work around a floating-point abi issue on mips

include/sys/prctl.h

@@ -119,6 +119,11 @@ struct prctl_mm_map {
 #define PR_MPX_ENABLE_MANAGEMENT  43
 #define PR_MPX_DISABLE_MANAGEMENT 44
 
+#define PR_SET_FP_MODE          45
+#define PR_GET_FP_MODE          46
+#define PR_FP_MODE_FR (1 << 0)
+#define PR_FP_MODE_FRE (1 << 1)
+
 int prctl (int, ...);
 
 #ifdef __cplusplus