Allow single-character keys for tEXt chunks
Allow single-character keys for tEXt chunks

The keys for tEXt chunks are documented as 1-79 character
ASCII strings. Testing this shows that we reject single-
character keys as too short. Fix that.

Distrotech/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,GNOME/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,Distrotech/gdk-pixbuf