OpenSystemsDevelopment / qpdf

Run this:

for i in  **/*.cc **/*.c **/*.h **/*.hh; do
  clang-format < $i >| $i.new && mv $i.new $i
done

The PDF spec only allows UTF-16BE, but most readers seem to accept
UTF-16LE as well, so now qpdf does too.

If we're opening a PDF file to copy its encryption information or
attachments, its version doesn't need to influence the output version.

This comment expands all tabs using an 8-character tab-width. You
should ignore this commit when using git blame or use git blame -w.

In the early days, I used to use tabs where possible for indentation,
since emacs did this automatically. In recent years, I have switched
to only using spaces, which means qpdf source code has been a mixture
of spaces and tabs. I have avoided cleaning this up because of not
wanting gratuitous whitespaces change to cloud the output of git
blame, but I changed my mind after discussing with users who view qpdf
source code in editors/IDEs that have other tab widths by default and
in light of the fact that I am planning to start applying automatic
code formatting soon.

Clarify that names are to appear in canonical form with PDF escaping
resolved when used in non-parsing QPDFObjectHandle APIs and their C
API counterparts. See https://github.com/qpdf/qpdf/discussions/625.

Replace PointerHolder arrays wherever it can be done without breaking ABI.

* Don't surprise people with deprecation warnings
* Provide detailed instructions and support for the transition

Create the typedefs directly in iterators rather than deriving from
the deprecated std::iterator class.

* Use unique_ptr in place of shared_ptr in some cases
* unique_ptr for arrays does not require a custom deleter
* use std::make_unique (c++14) where possible

None of these are in the public API.