Add missing since tags.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1479403 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/collections4/comparators/BooleanComparator.java

@@ -91,6 +91,7 @@ public final class BooleanComparator implements Comparator<Boolean>, Serializabl
      * @param trueFirst when <code>true</code>, sort
      * <code>true</code> <code>Boolean</code>s before <code>false</code>
      * @return a singleton BooleanComparator instance
+     * @since 4.0
      */
     public static BooleanComparator booleanComparator(final boolean trueFirst) {
         return trueFirst ? TRUE_FIRST : FALSE_FIRST;

src/main/java/org/apache/commons/collections4/comparators/ComparableComparator.java

@@ -58,6 +58,7 @@ public class ComparableComparator<E extends Comparable<? super E>> implements Co
      *
      * @param <E>  the element type
      * @return the singleton ComparableComparator
+     * @since 4.0
      */
     @SuppressWarnings("unchecked")
     public static <E extends Comparable<? super E>> ComparableComparator<E> comparableComparator() {