[x265] Encoder::encode(): don't return 0 while flushing.

[Derek Buitenhuis]

On 6/17/2014 8:03 AM, Satoshi Nakagawa wrote:
> using ffmpeg, when input sequence is shorter than lookahead, empty stream is
> encoded.

Should be fixed on my (FFmpeg's) end, using something akin to what
libx264 does:

https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/libx264.c;h=5d1e203a7fed11fd8160e31eec04a2e152117a5e;hb=HEAD#l265

- Derek