Log Message:
ffmpeg3: update to 3.1.5

- avformat/mxfdec: Check size to avoid integer overflow in mxf_read_utf16_string()
- avcodec/mpegvideo_enc: Clear mmx state in ff_mpv_reallocate_putbitbuffer()
- avcodec/utils: Clear MMX state before returning from avcodec_default_execute*()
- doc/examples/demuxing_decoding: Drop AVFrame->pts use
- libopenjpegenc: fix out-of-bounds reads when filling the edges
- libopenjpegenc: stop reusing image data buffer for openjpeg 2
- configure: fix detection of libopenjpeg
- doc: fix various typos and grammar errors
- avformat/utils: Update codec_id before using it in the parser init
- cmdutils: fix typos
- lavfi: fix typos
- lavc: fix typos
- tools: fix grammar error
- ffmpeg: remove unused and errorneous AVFrame timestamp check
- Support for MIPS cpu P6600
- avutil/mips/generic_macros_msa: rename macro variable which causes segfault \ 
for mips r6