OpenSystemsDevelopment / qpdf

To be encapsulated later.

Also, when recovering trailer from xref streams, pick the last valid
trailer encountered rather than the first.

In FUTURE, treat uninitialized object handles as null

Fixes fuzz issue 71689.

Change the return type to a std::pair<bool, QPDFObjectHandle> in order to
allow a default constructed object handle (which is currently returned to
indicate failure) to become a valid object.

Fix handling of hybrid reference files in QPDF::read_xrefTable

Fix #1242

Fix QPDF::recoverStreamLength

Tidy QPDF_Stream

Replace some std::shared_ptr parameters with reference parameters

Ensure QPDF m->all_pages and invalid_page_found are reset if
getAllPagesInternal throws an exception.

Fixes fuzz case 71624.

1. Make class final
2. Pass og parameter by value
3. Properly initialize qpdf and og

Also, tweak QPDF::replaceObject to allow stream replacement without
violating the requirement that streams must always be indirect objects.

Also, remove QPDF::reserveStream as it does not do what the name implies
and having this as a separate methods does not aid code readability.

Given that the PDF spec requires the xref table to contain entries for all
object ids <= the maximum id present in a PDF document, max_size is a
qpdf implementation limitation for legitimate object ids.

Refactor Pl_QPDFTokenizer

Ensure the the recovered stream end is not part of a different object.

Test file is bad24.pdf with stream 4 'endstream' corrupted.

QPDF::read_xrefTable ignores type 0 entries for objects in a section if an
associates XRefStm has an entry for the same object.

The spec states:

When the conforming reader searches for an object, if an entry is not
found in any given standard cross-reference section, the search shall
proceed to a cross-reference stream specified by the XRefStm entry
before looking in the previous cross-reference section,

If a deleted entry is found in a section, the XRefStm is not searched
according to the standard.