Needs review: [CALCITE-2278]

[Haisheng Yuan]

Hi Calcite commitors,
Issue CALCITE-2278 needs review, please kindly take a look at pull 
request:https://github.com/apache/calcite/pull/676
[CALCITE-2278] Fix bug that AggregateJoinTransposeRule fails to split aggcall 
for unique input with agg call.
Thanks ~Haisheng Yuan