A few minor things fell through the cracks of previously landed cls:
- Added missing ops from TOutputTraverser::visitAggregate
- Made sure some members were initialized in TIntermAggregate
- Removed UNIMPLEMENTED() for implemented feature

Change-Id: Iec139533714ad6288f2f3962873616b5578a0ceb
Reviewed-on: https://swiftshader-review.googlesource.com/5480Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>