core/asm: Allow JUMP with no argument

This way, a label can be pushed explicitly, or loaded from memory to
implement a jump table.

core/asm/compiler.go

@@ -186,6 +186,8 @@ func (c *Compiler) compileElement(element token) error {
 			pos := big.NewInt(int64(c.labels[rvalue.text])).Bytes()
 			pos = append(make([]byte, 4-len(pos)), pos...)
 			c.pushBin(pos)
+		case lineEnd:
+			c.pos--
 		default:
 			return compileErr(rvalue, rvalue.text, "number, string or label")
 		}

core/asm/compiler_test.go

@@ -39,6 +39,21 @@ func TestCompiler(t *testing.T) {
 `,
 			output: "63000000055b",
 		},
+		{
+			input: `
+	PUSH @label
+	JUMP
+	label:
+`,
+			output: "6300000006565b",
+		},
+		{
+			input: `
+	JUMP @label
+	label:
+`,
+			output: "6300000006565b",
+		},
 	}
 	for _, test := range tests {
 		ch := Lex([]byte(test.input), false)