runtime: fix freebsd-amd64 (and part of 386)

R=rsc
CC=golang-dev
https://golang.org/cl/4285063
diff --git a/src/pkg/runtime/freebsd/amd64/defs.h b/src/pkg/runtime/freebsd/amd64/defs.h
index 2a295a4..b101b19 100644
--- a/src/pkg/runtime/freebsd/amd64/defs.h
+++ b/src/pkg/runtime/freebsd/amd64/defs.h
@@ -61,6 +61,9 @@
 	BUS_OBJERR = 0x3,
 	SEGV_MAPERR = 0x1,
 	SEGV_ACCERR = 0x2,
+	ITIMER_REAL = 0,
+	ITIMER_VIRTUAL = 0x1,
+	ITIMER_PROF = 0x2,
 };
 
 // Types
@@ -83,7 +86,7 @@
 	int64 *child_tid;
 	int64 *parent_tid;
 	int32 flags;
-	byte pad0[4];
+	byte pad_godefs_0[4];
 	Rtprio *rtp;
 	void* spare[3];
 };
@@ -93,7 +96,7 @@
 	int8 *ss_sp;
 	uint64 ss_size;
 	int32 ss_flags;
-	byte pad0[4];
+	byte pad_godefs_0[4];
 };
 
 typedef struct Sigset Sigset;
@@ -114,7 +117,7 @@
 	int8 *ss_sp;
 	uint64 ss_size;
 	int32 ss_flags;
-	byte pad0[4];
+	byte pad_godefs_0[4];
 };
 
 typedef struct Siginfo Siginfo;
@@ -178,6 +181,18 @@
 	StackT uc_stack;
 	int32 uc_flags;
 	int32 __spare__[4];
-	byte pad0[12];
+	byte pad_godefs_0[12];
+};
+
+typedef struct Timeval Timeval;
+struct Timeval {
+	int64 tv_sec;
+	int64 tv_usec;
+};
+
+typedef struct Itimerval Itimerval;
+struct Itimerval {
+	Timeval it_interval;
+	Timeval it_value;
 };
 #pragma pack off