Add support for Commons-Lang's RandomUtils

This is realised by somewhat generalising our interfaces for modelling RNGs. We also add tests for randomness-related queries that didn't have any, and addtest cases checking the Apache random-number generators are interchangeable with the stdlib ones.

java/ql/test/query-tests/BadAbsOfRandom/Test.java

@@ -0,0 +1,20 @@
+import java.util.Random;
+import org.apache.commons.lang3.RandomUtils;
+
+public class Test {
+
+  public static void test() {
+
+    Random r = new Random();
+    Math.abs(r.nextInt());
+    Math.abs(r.nextLong());
+    Math.abs(r.nextInt(100)); // GOOD: random value already has a restricted range
+
+    Math.abs(RandomUtils.nextInt());
+    Math.abs(RandomUtils.nextLong());
+    Math.abs(RandomUtils.nextInt(1, 10)); // GOOD: random value already has a restricted range
+    Math.abs(RandomUtils.nextLong(1, 10)); // GOOD: random value already has a restricted range
+
+  }
+
+}