OpenSystemsDevelopment / qpdf

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

Fix #1242

Tidy QPDF_Stream

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.

Refactor Pl_QPDFTokenizer

Create unresolved objects only for objects in the xref table (except during
parsing of the xref table). Do not add indirect nulls into the the object
cache as the result of a cache miss during a call to getObject except
during parsing or creation/updating from JSON. To support this behaviour,
add new private methods getObjectForParser and getObjectForJSON.

As a result of this change, dangling references are treated as direct nulls
rather than indirect nulls.

Buffer output locally.
Add qpdf_fuzzer test case.

In FUTURE make various QPDFObjectHandle methods const

Throw damagedFile if max_warnings is exceeded. Change qpdf_fuzzer warnings limit to
limit to 500.

As a rule, we should avoid conditional compilation is it always causes
code paths that are sometimes not even seen lexically by the compiler.
Also, we want the actual code being fuzzed to be as close as possible
to the real code. Conditional compilation is suitable to handle
underlying system differences.

Instead, favor configuration using callbacks or other methods that can
be triggered in the places where they need to be exercised.

Ensure objects with impossibly large ids are ignored.

Also, apply limit in dct_fuzzer

Amend fuzz future

Refactor QPDF::parse_xrefEntry

QPDF::processXRefStream