Add missing @since tags for new API methods

Change-Id: I38f10d622c30f19d1154a4901477e844cb411707
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/lib/RefUpdate.java

@@ -638,6 +638,7 @@ public abstract class RefUpdate {
 	 * are checked explicitly.
 	 *
 	 * @param check
+	 * @since 3.0
 	 */
 	public void setCheckConflicting(boolean check) {
 		checkConflicting = check;

org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackConfig.java

@@ -379,6 +379,7 @@ public class PackConfig {
 	 * @return true if existing delta chains should be cut at
 	 *         {@link #getMaxDeltaDepth()}. Default is false, allowing existing
 	 *         chains to be of any length.
+	 * @since 3.0
 	 */
 	public boolean getCutDeltaChains() {
 		return cutDeltaChains;
@@ -395,6 +396,7 @@ public class PackConfig {
 	 *
 	 * @param cut
 	 *            true to cut existing chains.
+	 * @since 3.0
 	 */
 	public void setCutDeltaChains(boolean cut) {
 		cutDeltaChains = cut;