Big day in poppler-land

Today in Poppler:
* Poppler 0.57 got released
* We agreed to stop supporting openjpeg 1.x at the end of the year
* We agreed to stop supporting Qt 4.x at the end of the year
* We merged the better_object branch

The last one is the one that is really big, since it introduces a big rework of the Object class, a central component to Poppler. Object is much used like a QVariant, i.e. it can hold various kind of data inside and you can pass it around.

Unfortunately the Object implementation we inherited from xpdf was kind of hard to use, having to basically do the memory management by hand. i.e. destroying the object was not enough to free the memory, you had to call free() on it.

Thanks to C++11 now we have an implementation with move semantics that greatly simplifies the use of Object and will hopefully make for less memory management mistakes.

Let's hope we didn't break anything in the process though :D