implicit sbr + ps not working

[dieterstueken]

I failed to decode any he-aac plus v2 (AAC + SBR + PS) stream.
After several nights of debugging against faad2 (C-code) I found several bugs.
Concerning SBR I prepared a pull request.
Implicit PS did not work, too. The function SBR.processPS() was not called at all.
The output channel is prepared as mono and can not be switched to stereo easily.
As a workaround I upgraded all mono streams to stereo.
All the bugs I found in the original code too.

Dieter.