epeg_open_header failes for some jpgs

[manuelstofer]

The iteration over im->in.jinfo.marker_list seems to be broken.
https://github.com/mattes/epeg/blob/master/src/lib/epeg_main.c#L838

This return statement returns always after the first marker.
https://github.com/mattes/epeg/blob/master/src/lib/epeg_main.c#L902

[manuelstofer]

Made a pull request #12, so I'm closing this.

[mattes]

Thanks!