avformat/img2dec: Support -loop with pipes

Fixes Ticket3976

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 684508ba15ca15d5d43f67bbed483ce5b6617f10)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/img2dec: Attempt to detect non-escaped glob patterns too (-pattern_type glob)

Fixes ticket #3948

Based-on-patch-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Alexander Strasser <eclipse7@gmx.net>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit e079d43af86c38a0c0efb9bc6058e1316e6a18f4)

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