1. Old logic meaned: everywhere, except Windows, ffmpeg has to use HW
acceleration, but on Windows ffmpeg has to use (unavailable) software
HEVC by default
2. Software HEVC is available only if you provide corresponding
software MediaSDK library, which isn't provided with ffmpeg. More
information could be found in
https://github.com/Intel-Media-SDK/MediaSDK/blob/master/doc/samples/readme-encode_linux.pdf
3. HW HEVC decoding/encoding are available on Windows in the driver by default

Note: Default case should be the most common case but this change still has potential risk
on windows if HW path is not supported(or doesn't work as expection).
(See the historical disscution: https://lists.libav.org/pipermail/libav-devel/2016-November/080419.html).
In such case, two options suggested:
1. Use the option "-load_plugin hevc_sw" to switch SW path manually.
2. Or report bug to Intel windows driver if your GPU can support HEVC HW codec.
  (HEVC decoding is supported since Braswell, and encoding supported since Skylake)

Patch started by Landgraph. Add similar change for hevc decoder and bump a new version.
Reviewed-by: Mark Thompson <sw@jkqxz.net>
Reviewed-by: Maxym Dmytrychenko <maxim.d33@gmail.com>
Signed-off-by: Landgraph <me@landgraph.ru>
Signed-off-by: Zhong Li <zhong.li@intel.com>