media/codec: add of h265 (with hardware acceleration only)

contrib/src/ffmpeg/rules.mak

src/account.cpp

src/account.h

src/client/videomanager.cpp

src/jamidht/jamiaccount.cpp

src/media/media_encoder.cpp

src/media/media_encoder.h

src/media/system_codec_container.cpp

src/media/system_codec_container.h

src/media/video/accel.cpp