Add util for unsigned and signed int. conversion

Will be used in later commit in extended clipboard handling.

core/util/int.js

@@ -0,0 +1,15 @@
+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2020 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ */
+
+export function toUnsigned32bit(toConvert) {
+    return toConvert >>> 0;
+}
+
+export function toSigned32bit(toConvert) {
+    return toConvert | 0;
+}

tests/test.int.js

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+/* eslint-disable no-console */
+const expect = chai.expect;
+
+import { toUnsigned32bit, toSigned32bit } from '../core/util/int.js';
+
+describe('Integer casting', function () {
+    it('should cast unsigned to signed', function () {
+        let expected = 4294967286;
+        expect(toUnsigned32bit(-10)).to.equal(expected);
+    });
+
+    it('should cast signed to unsigned', function () {
+        let expected = -10;
+        expect(toSigned32bit(4294967286)).to.equal(expected);
+    });
+});