OpenSystemsDevelopment / qpdf

- Remove unnecessary QPDF_DLLs
- make deleted constructors public
- move some comments to support tooltips
- modernise some constructors and destructors
- change some member shared pointers to unique pointers

Register crypto

Clean up comments in QPDFObject.hh

Refactor QPDFObject / QPDFObjectHandle

Move all stream-specific methods to new class qpdf::Stream

Move all array-specific methods to new class qpdf::Array.

Move all dictionary specific methods to BaseDictionary. Create new subclass
Dictionary to allow QPDFObjectHandle to access the moved methods.

Replace data member oh with accessors.

Remove redundant overloads from QPDFObjGen::set.

The new class is only usable as base classes and does not support direct
instantiation or upcasting.

Add operators to convert to bool, QPDFObjectHandle and QPDFObjGen.

Derive QPDFObjectHandle from BaseHandle and make final.

Remove more deprecated API

Refine QPDFParser error handling

#1349 introduced a limit on the maximum size of arrays and dictionaries
contained in objects that generate errors during parsing, and #1354
reduced that limit to 5000 objects. However, the limit was only imposed
once a further error was encountered.

Stop adding objects to containers once the limit is reached.

Fixes oss-fuzz issue 398060137

Tune JSON::JSON_string

Fix typo in usage for fix-qdf

Deprecate QPDFTokenizer push mode

Remove member encoded and encode strings only when required.

Encoded is only used when writing JSON. Since most JSON writing is now
done on the fly without creating a JSON representation, creating and
storing the encoded string in almost all cases no longer serves any
purpose.

Push mode is not used by qpdf and is not tested. It is difficult to see a
legitimate use for it.

Continuing to support it creates unnecessary constraints and effort when
adapting the tokenizer.

Discontinue ChangeLog; update release notes as you go