This commit ports the following from aom/master:
4c46278 Add aom_reader_tell() support.
b9c9935 Remove an erroneous declaration.
56c9c3b Fix ANS build.
Change-Id: I59bd910f58c218c649a1de2a7b5fae0397e13cb1
Reconciles the following commits from aom/master to nextgenv2:
- 25aaf40bbc24beeb52de9af7d7624b7d7c6ce9de
- 87073de5693df70eba1c9b9be2b2732ed3b08fb3
Change-Id: Ideda50a6ec75485cb4fa7437c69f4e58d6a2ca73