OpenSystemsDevelopment / qpdf

Also, test writing JSON v1 files and files with deeply nested containers.

Provide a custom method to check whether a name is valid utf8. Integrate
checking for characters that need to be escaped in JSON.

Create an alternative to getJSON to allow an object handle to be written as JSON without the overhead of creating a JSON object.

Create a simple utility class for writing JSON to a pipeline.

...as well as some cases generated in CI from earlier attempts at
fixing this.

A parse error in stream data in which stream data contained a nested
object would cause a crash because qpdf was not correctly updating its
internal state. Rework the QPDF json reactor to not be sensitive to
parse errors in this way.

Allow "n:/pdf-syntax" JSON syntax for dictionary keys

Update TODO.md regarding indirect nulls in QPDF_Dictionary

Also, modernize for loop.

Instead of overwriting cur_row.data() use clear and insert.

Tighten checks for invalid indirect references  during xref reconstru…

Handle default-constructed JSON objects

Tighten checks for invalid indirect references in QPDFParser

Update .clang-format to require braces after control statements

Fix incorrect handling of invalid negative object ids

Fix two errors introduced in #1110 and #1112. Since
#1110, encountering the invalid indirect reference #1110
-2147483648 n R produces an integer underflow which, if
 undetected, immediately trigger a logic error. Since
 #1112, object -1 0 R may be incorrectly identified as
 an earlier generation of itself and deleted,
 invalidating a live iterator.