omx_vp8dec: Component to report Role as video_decoder.vp8

This is the correct role to report, vpx is legacy and should not
be used anymore

Signed-off-by: Daniel Charles <daniel.charles@intel.com>
VideoEncoderAVC: use %p to print pointer
encoderbase: protect android with ifdef
EncoderBase: need overide to call start in base class
encoder: add avc encoder
OMXVideoDecoderBase: fix frame lost upon EOS

1. it's up to the omxil client (gst-omx for example) to repeately/actively
   retrieve all the decoded buffer after EOS reach input port
2. it's up to the codec lib (libyami for example) to set
   all the cached frame to be outputable
3. omx retains the input buffer (empty buffer with EOS) until there is
   not any output buffer available from decoder