feat: display edit history diff (#922)

* build: add google's diff-match-patch

Copied from 62f2e689f4/java/src/name/fraser/neil/plaintext/diff_match_patch.java

* feat(status/edit-history): display diff for text

Closes https://github.com/sk22/megalodon/issues/789

* fix(status/edit-history): add fake poll id

* code style adjustments

* don't diff if only formatting changed

---------

Co-authored-by: sk <sk22@mailbox.org>

mastodon/src/main/java/org/joinmastodon/android/api/requests/statuses/GetStatusEditHistory.java

@@ -26,6 +26,8 @@ public class GetStatusEditHistory extends MastodonAPIRequest<List<Status>>{
 			s.visibility=StatusPrivacy.PUBLIC;
 			s.mentions=Collections.emptyList();
 			s.tags=Collections.emptyList();
+			if (s.poll != null)
+				s.poll.id="fakeID"+i;
 			i++;
 		}
 		super.validateAndPostprocessResponse(respObj, httpResponse);