removed obsolete configure option

Closes https://github.com/mate-desktop/atril/pull/112
ePub backend: unescape uri strings from toc

Toc may include links with strings escaped for URI format. We needed to un-escape them.
ePub: Can open documents which do not have toc

I always thought all ePub documents had either a traditional ncx or an epub3 nav. Now as it turns out,
sometimes neither of these are present. Fixed.
don't leak memory
don't leak memory, pt.2
don't leak memory, pt.3
don't leak memory, pt.4
don't leak memory, pt.5
don't leak memory, pt.6
don't leak memory, pt.7