OpenSystemsDevelopment / qpdf

This required moving some newly inlined functions back to the cc file,
but that seems to have had no measurable performance impact.

Avd xcsv brvtns.

Tidy QPDF::getAllPagesInternal and QPDF::pushInheritedAttributesToPageInternal

Also, modify QPDFObject::swapWith to update the ObjGens of the swapped
objects.

Modify QPDF::newIndirect and QPDF::updateCache to keep object ObjGens
up to date.

Modify QPDFParser::parse to call QPDF::getObject instead.

Add a new obj_cache entry or update an existing entry in place.

Also change QPDF::replaceObject and QPDF::swapObjects such that the
QPDFObject assigned to an og in the obj_cache is never replaced; only
QPDFObject::value is updated.

Centralise casting of QPDFObjects and reduce repeated dereferencing.

Allow QPDFObjectHandle::obj to be set prior resolving object.

ot_unresolved has been appended to the list object types in order to
preserve the output of existing test cases.

Report mem usage

Part of #729

Part of #729

Part of #729

Add optional parameter allow_nullptr to QPDFObjectHandle::getOwningQPDF

Also, inline method and add optional parameter error_msg.

Provide buffered input for QPDFTokenizer.