Moved sizeof functions to a separate package

src/build/sizeof/Unsigned.go

@@ -0,0 +1,20 @@
+package sizeof
+
+import "math"
+
+// Unsigned tells you how many bytes are needed to encode this unsigned number.
+func Unsigned(number uint64) int {
+	switch {
+	case number <= math.MaxUint8:
+		return 1
+
+	case number <= math.MaxUint16:
+		return 2
+
+	case number <= math.MaxUint32:
+		return 4
+
+	default:
+		return 8
+	}
+}