OpenSystemsDevelopment / qpdf

With docbook, this was not converted properly in the PDF version, but
since we are moving out of docbook, we can just put the Unicode
character in the source.

Footnotes are yucky in online documentation, and the one footnote in
the doc is no longer needed, so remove it.

Make a list of things that need to be done while converting docbook to
sphinx/rst.

* Make it a runtime error, not a logic error
* Include additional information
* Capture it properly in checkLinearization

* Handle error conditions that occur when using the object handle
  interfaces. In the past, some exceptions were not correctly
  converted to errors or warnings.
* Add more detailed information to qpdf-c.h
* Make it possible to work more explicitly with uninitialized objects

It was exercised in the pdf-linearize example but not in qpdf-ctest.

Thanks for the nudge from m-holger!

The impact on the code would be extremely high, and using it would
clutter the code greatly because it would break chaining like
a.getKey("/B").getKey("/C"). There are better ways to deal with the
issue.

Return new qpdf_oh from qpdf_oh_wrap_in_array when input is already an array.
Update some doc comments in qpdf-c.h.

Fix typo in --rotate example

Don't assume endobj is at the beginning of the line. This means we are
looking at tokens for every line, but the odds of n n obj appearing in
the middle of the object are likely much lower than endobj not being
at the beginning of the line or missing entirely. This will probably
have a negative impact on recovery time for very large files.
Hopefully it will be worth it.

Main branch is `main` now

Thanks @neuhaus!