OpenSystemsDevelopment / qpdf

…or deterministic ID generation (fixes #1235).

…evel` and add `const&` to `child` parameter.

…, improving encapsulation and memory management. Remove the now redundant `pushMD5Pipeline` method and streamline MD5 activation.

…te encryption handling

…ify pipeline stack management

Encapsulated pipeline stack management into a dedicated `Pl_stack` class within `QPDFWriter::Members`. Reorganized related methods to streamline and simplify initialization and activation of pipelines, removing redundant code.

…dundant normalization and string unparse logic across multiple write calls.

… overloads, streamline QDF handling, and simplify string and trailer writes.

…ased logic in `setEncryptionMinimumVersion`, and reduce redundancy across `QPDFWriter` methods.

…`, simplify method signatures, and centralize logic in `QPDF::EncryptionData` for improved maintainability.

…ng in method parameters, and simplify encryption logic for improved maintainability and reduced redundancy.

…uce redundancy, improve maintainability, and streamline parameter handling.

... and use it in QPDFWriter and QPDF::generateHintStream.

Also, remove redundant QPDFWriter::writeBuffer.

Also,
- use Pl_Discard when only checking whether stream is filterable
- get last char directly from output string

- 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

Except for virtual functions to avoid the need for users to update code.

Also, uninitialize QPDFWriter::Members members.