fmt.Scan: fix integer overflow on 32-bit machines

R=r, rsc
CC=golang-dev
https://golang.org/cl/2144043

src/pkg/fmt/scan.go

@@ -740,7 +740,7 @@ func (s *ss) scanOne(verb int, field interface{}) {
 	case *int32:
 		*v = int32(s.scanInt(verb, 32))
 	case *int64:
-		*v = s.scanInt(verb, intBits)
+		*v = s.scanInt(verb, 64)
 	case *uint:
 		*v = uint(s.scanUint(verb, intBits))
 	case *uint8:

src/pkg/fmt/scan_test.go

@@ -183,6 +183,9 @@ var scanTests = []ScanTest{
 
 	// Custom scanner.
 	ScanTest{"  vvv ", &xVal, Xs("vvv")},
+
+	// Fixed bugs
+	ScanTest{"2147483648\n", &int64Val, int64(2147483648)}, // was: integer overflow
 }
 
 var scanfTests = []ScanfTest{