Flexibilize Util.parseXsDateTime to allow single digit hour

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=156999955

library/core/src/androidTest/java/com/google/android/exoplayer2/util/UtilTest.java

@@ -146,6 +146,7 @@ public class UtilTest extends TestCase {
     assertEquals(1411161535000L, Util.parseXsDateTime("2014-09-19T13:18:55-08:00"));
     assertEquals(1411161535000L, Util.parseXsDateTime("2014-09-19T13:18:55-0800"));
     assertEquals(1411161535000L, Util.parseXsDateTime("2014-09-19T13:18:55.000-0800"));
+    assertEquals(1411161535000L, Util.parseXsDateTime("2014-09-19T13:18:55.000-800"));
   }
 
   public void testUnescapeInvalidFileName() {

library/core/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -98,7 +98,7 @@ public final class Util {
   private static final Pattern XS_DATE_TIME_PATTERN = Pattern.compile(
       "(\\d\\d\\d\\d)\\-(\\d\\d)\\-(\\d\\d)[Tt]"
       + "(\\d\\d):(\\d\\d):(\\d\\d)([\\.,](\\d+))?"
-      + "([Zz]|((\\+|\\-)(\\d\\d):?(\\d\\d)))?");
+      + "([Zz]|((\\+|\\-)(\\d?\\d):?(\\d\\d)))?");
   private static final Pattern XS_DURATION_PATTERN =
       Pattern.compile("^(-)?P(([0-9]*)Y)?(([0-9]*)M)?(([0-9]*)D)?"
           + "(T(([0-9]*)H)?(([0-9]*)M)?(([0-9.]*)S)?)?$");