stagefright: Expose decoder extradata via native MediaCodec

Stash GraphicBuffer in filled output so the clients of
native MediaCodec (during surface-mode playback) can retrieve
buffer information; not limited to dimensions, color-
format, decoded YUV data (including trailing extradata)...

User Extradata can be requested by setting
"enable-extradata-user" in the configuration format.

Change-Id: Iaa49f448a9692e1c1dfe037ea71ddeef73d14d66