gc: fix arm build

R=ken2
CC=golang-dev
https://golang.org/cl/3074041

src/cmd/gc/builtin.c.boot

@@ -86,7 +86,9 @@ char *runtimeimport =
 	"func \"\".int64mod (? int64, ? int64) int64\n"
 	"func \"\".uint64mod (? uint64, ? uint64) uint64\n"
 	"func \"\".float64toint64 (? float64) int64\n"
+	"func \"\".float64touint64 (? float64) uint64\n"
 	"func \"\".int64tofloat64 (? int64) float64\n"
+	"func \"\".uint64tofloat64 (? uint64) float64\n"
 	"func \"\".complex128div (num complex128, den complex128) complex128\n"
 	"\n"
 	"$$\n";

src/cmd/gc/runtime.go

@@ -117,6 +117,8 @@ func uint64div(uint64, uint64) uint64
 func int64mod(int64, int64) int64
 func uint64mod(uint64, uint64) uint64
 func float64toint64(float64) int64
+func float64touint64(float64) uint64
 func int64tofloat64(int64) float64
+func uint64tofloat64(uint64) float64
 
 func complex128div(num complex128, den complex128) (quo complex128)