OpenSystemsDevelopment / qpdf

Add optional parameter allow_nullptr to QPDFObjectHandle::getOwningQPDF

Also, inline method and add optional parameter error_msg.

Provide buffered input for QPDFTokenizer.

This results in measurable performance improvements to packaged binary
libqpdf distributions. QTC remains available for library users and is
still selectively enabled in CI.

This is a guess...I'm not sure exactly why there are linker issues or
how to reproduce them.

Add QPDF::getObject to replace getObjectByObjGen and getObjectByID

For consistency with similar methods, e.g. replaceObject.

Also, make QPDFObjectHandle::isIndirect const.

Now --json-output just changes defaults. Allow output file with --json.

from "qpdf-v2" to "qpdf": [..., ...]

Add additional parameters that will be needed to call QPDF::writeJSON
in partial mode.

When the schema wants a variable-length array, allow a single item as
well as allowing an array.