Fix searching for end of inline (EI) images with ASCII85Decode filters (bug 1077808)

Based on http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/PDF32000_2008.pdf#page=33, this is a tentative patch to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1077808.




Thinking out loud: I don't remember if you need to ignore `(0xFF 0xFF)*2 0xF9` sequences