OpenSystemsDevelopment / qpdf

Also, add const overload of QPDFObjectHandle::getObj

Stop using nullptr to represent null objects.
Count null array elements and trigger creation of sparse arrays if null count is
greater than 100.

Add temporary clone of SparseOHArray  to implement non-sparse mode.

Warn if catalog type entry is invalid (fixes #810)

Improve --optimize-images to find images nested within XObjects

Refactor QdfFixer::processLines

Remove redundant parameter depth from QPDF::updateObjectMaps

Add new data member QPDFWriter::Members::root_og

Also, uninitialize QPDFWriter::Members members.

Also, change QPDFJob to use unique_ptr<QPDF> instead of shared pointers.

At the end of importing a JSON file, scan the object cache for reserved
objects and replace with null objects.

Recognise that JSON objects are effectively shared pointers to JSON_value.

Refactor setting of object descriptions in QPDF::JSONReactor

Refactor creation of object descriptions

Eliminate the use of shared pointers in JSONParser

Allow access to private header files when defining data members.