Update ArrayMap.java

Came across an error when iterating over the entries of an ArrayMap. Used to point to the same Entry-Instance each time with updated values only. This results in unwanted changes in priorly assigned Entry-Instances. See example:
```
    private void testIterable() {

		TestIterable t = new TestIterable();
		for (Entry<Integer, String> e : t) {
			System.out.println(e.key + "=" + e.value);
		}
		
		Entry<Integer, String> first = null;
		Entry<Integer, String> second = null;
		Entry<Integer, String> third = null;
		int index = 0;
		
		for (Entry<Integer, String> e : t) {
			
			if (index == 0) {
				first = e;
			}
			if (index == 1) {
				second = e;
			}
			if (index == 2) {
				third = e;
			}
			index++;
		}
		
		System.out.println("FIRST: " + first + " SECOND: " + second + "THIRD: " + third);
		System.out.println("Should have been: ");
		System.out.println("FIRST: 1=aaa SECOND: 2=bbb THIRD: 3=ccc");
	}

	class TestIterable implements Iterable<Entry<Integer, String>> {

		com.badlogic.gdx.utils.ArrayMap<Integer, String> map = new com.badlogic.gdx.utils.ArrayMap<Integer, String>();
		int iterate = 0;
		
		public TestIterable() {
			
			map.put(0, "aaa");
			map.put(1, "bbb");
			map.put(3, "ccc");
		}
		
		@Override
		public Iterator<Entry<Integer, String>> iterator() {
			
			return map.entries();
		}
	}
```
PS: I am new to GitHub and wrote this (and the code) on the webpage. Hope it works though...