Fix Travis to really test 32 bits

To make sure 32 bits arch is being tested, try the following test which should
fail in 32 bits mode:
```go
package utils

import (
	"math/bits"
	"testing"
)

func TestBreak(t *testing.T) {
	if bits.UintSize != 64 {
		panic("bits.UintSize != 64")
	}
}
```

.travis.yml

@@ -22,4 +22,4 @@ before_install:
   - export GOARCH=$XGOARCH
 
 script:
-  - GOARCH=$XGOARCH go test -v ./...
+  - go test -v ./...

utils/break_test.go

@@ -1,12 +0,0 @@
-package utils
-
-import (
-	"math/bits"
-	"testing"
-)
-
-func TestBreak(t *testing.T) {
-	if bits.UintSize != 64 {
-		panic("bits.UintSize != 64")
-	}
-}

utils/showarchbits_test.go

@@ -0,0 +1,11 @@
+package utils
+
+import (
+	"fmt"
+	"math/bits"
+	"testing"
+)
+
+func TestShowArchBits(t *testing.T) {
+	fmt.Printf("Architecture is %v bits\n", bits.UintSize)
+}