Merge remote-tracking branch 'lukaszmluki/master'

* lukaszmluki/master:
  lavd/avdevice: always free detected devices on error
  lavf/http: return error from seek on invalid whence
  lavf/http: return error on seeking to negative postion
  lavf/avio: fix ffurl_alloc error checks

Merged-by: Michael Niedermayer <michaelni@gmx.at>

diff --cc libavformat/http.c
Simple merge