set execution bit for /etc/vdr/recording-hooks/R90.custom

See http://www.vdr-portal.de/board16-video-disk-recorder/board99-distributionen/board96-yavdr/p1165078-gel%C3%B6st-recording-hook-zieht-nicht/#post1165078
Merge pull request #1 from seahawk1986/patch-1

set execution bit for /etc/vdr/recording-hooks/R90.custom