avconv_opt: fix avio_open2() return code check

avio_open2() only return < 0 when error.
dnxhdenc: return meaningful return codes
avconv: make the ASCII flow charts narrower to fit onto TTY

These charts in man page are currently destroyed.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Merge commit '9e4e35b4d7c43a908944183a58aa389a23116fd6'

* commit '9e4e35b4d7c43a908944183a58aa389a23116fd6':
  avconv_opt: fix avio_open2() return code check

See: 774239be717150909219ad2c0696bfb6a50cf2cb
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '68e95ab81be1aa3f47ab148dceb8711ef5f4212d'

* commit '68e95ab81be1aa3f47ab148dceb8711ef5f4212d':
  dnxhdenc: return meaningful return codes

Conflicts:
	libavcodec/dnxhdenc.c

See: b9bedb0b287d3aaa30540d18fdb87b2cc98ca339
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  avconv: make the ASCII flow charts narrower to fit onto TTY

Conflicts:
	doc/ffmpeg.texi

See: 8fe107609437909ddd2cf8f5690fe0158a0616f2
Merged-by: Michael Niedermayer <michaelni@gmx.at>
doc/indevs: Fix example for QTKit usage.

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