Log Message:
Update gstreamer1 and its plugins to 1.8.1.

Switch gst-plugin1-libav from ffmpeg2 to ffmpeg3.

1.8.1

The first 1.8 bug-fix release (1.8.1) was released on 20 April 2016.
This release only contains bugfixes and it should be safe to update
from 1.8.0.

Major bugfixes in 1.8.1

    Fix app compilation with Android NDK r11 and newer
    Fix compilation of nvenc plugin against latest NVIDIA SDK 6.0
    Fix regression in avdeinterlace
    Fix memory corruption in scaletempo element with S16 input
    Fix glitches at the start with all audio sinks except for pulsesink
    Fix regression with encrypted HLS streams
    Fix automatic multithreaded decoding of VP8/9 video
    Fix deadlock in HTTP adaptive streams when scrub-seeking
    Fix regression in RTSP source with SRTP
    Add support for SRTP rollover counters in the RTSP source
    Add support for HiDPI ("Retina") screens in caopengllayersink
    ... and many more!