Reorganized file structure

src/build/cpu/Register.go

@@ -0,0 +1,11 @@
+package cpu
+
+import "fmt"
+
+// Register represents the number of the register.
+type Register uint8
+
+// String returns the human readable name of the register.
+func (r Register) String() string {
+	return fmt.Sprintf("r%d", r)
+}