vaapipic: base for encoder and decoder picture
decoderbase: allocate surface from pool
decoderbase: add outputPicture
vp8dec: use smart ptr
jpegdec: use smart pointers
decbase: add createPicture
h264dec: use smart ptr
h264dpb: init invalid buffer to NULL in reflist
decpicture: use std::pair instead VaapiDecSlice
VaapiEncPicture: derived from VaapiPicture
h264dec: do not use INT_MAX for poc, the type is int32_t