Implemented data labels

src/build/asm/RegisterNumber.go

@@ -16,3 +16,14 @@ type RegisterNumber struct {
 func (data *RegisterNumber) String() string {
 	return fmt.Sprintf("%s, %d", data.Register, data.Number)
 }
+
+// RegisterNumber adds an instruction with a register and a number.
+func (a *Assembler) RegisterNumber(mnemonic Mnemonic, reg cpu.Register, number int) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: mnemonic,
+		Data: &RegisterNumber{
+			Register: reg,
+			Number:   number,
+		},
+	})
+}