vf_drawtext: Do not leak the mmapped textfile

And validate its size while at it.

CC: libav-stable@libav.org
Bug-Id: CID 1244189
vf_showinfo: Forward the av_image_get_linesize error

CC: libav-stable@libav.org
Bug-Id: CID 1087086
af_resample: check av_opt_set_dict return value

CC: libav-stable@libav.org
Bug-Id: CID 1087076
avresample: prevent theoretical division by zero

CC: libav-stable@libav.org
Bug-Id: CID 1231986
avresample: Make sure the even check does not overflow

CC: libav-stable@libav.org
Bug-Id: CID 732225
oss_audio: use a macro to simplify ioctl() error checking

Also add a note about SNDCTL_DSP_GETFMTS which may fail even if OSS is
available.

CC: libav-stable@libav.org
Bug-Id: CID 1238992
Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
swscale: fix sign extensions in yuv planar conversion

Casting the left-most byte to unsigned avoids an undefined
result of the shift by 24 if bit 7 is set.

yuvPlanartouyvy_c and yuvPlanartoyuy2_c are affected.

CC: libav-stable@libav.org
Bug-Id: CID 732281 / CID 732282