interface: move host interface out of YamiMediaCodec namespace

move VideoDecoderHost/VideoEncoderHost interface/implementation
out of YamiMediaCodec namespace.
so, dlopen/dlsym can access the functions
compile: remove some warnings
interface: add preSandboxInit for chromeos support
h264enc: add forceKeyFrame support
h264enc: add setParameters support for framerate/bitrate
h264enc: add getMaxOutSize support
encoder: set input buffer reusable after data upload
h264enc: add flags support for encoded frames
h264enc: getOutput can be called in a separate thread
h264enc: limit buffer count in output queue

it balance the load of input/output threads,
avoid driver holds too much frames.
encoder: add rate control to VAConfig
h264enc: implement rate control
decoder: add timestamp in getOutput (when rendering to Drawable)
h264enc: support VideoConfigTypeAVCIntraPeriod

it gives client more option on bitrate control
fix: fix for getOutput(drawable, ...)