OpenSystemsDevelopment / qpdf

Preparing to change the class name back to QPDFObject

Also, since it's just there for compatibility, we don't need to add
new object types to it.

* Just removing a header file would cause build errors with no hint as
  to what happened. This way, people get a warning rather than error
  for the life of qpdf 11, and the warning tells them what to do.

* This avoids build surprises resulting from having two versions of
  QPDF headers installed at once. If you were building code out of a
  checkout of qpdf but had an older version installed on your system,
  if your code included <qpdf/QPDFObject.hh>, everything would work,
  but then your code would break without QPDFObject.hh later.

Also, modify QPDFObject::swapWith to update the ObjGens of the swapped
objects.

Modify QPDF::newIndirect and QPDF::updateCache to keep object ObjGens
up to date.

Allow QPDFObjectHandle::obj to be set prior resolving object.

ot_unresolved has been appended to the list object types in order to
preserve the output of existing test cases.

Move responsibility for creating shared pointers to objects and cloning from QPDFObjectHandle to QPDFObject.

Update getJSON() methods and calls to them

Run this:

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

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.

They have to be ot_* rather than qpdf_ot_* for compatibility.

* Different enumerated types are not assignment-compatible in C++, at
  least with strict compiler settings
* While you can do `constexpr ot_xyz = ::qpdf_ot_xyz` in QPDFObject.hh to
  make QPDFObject::ot_xyz work, QPDFObject::object_type_e::ot_xyz will
  only work if the enumerated type names are the same.

This is needed for some compilers on some platforms, notably current
versions of clang.

A few public destructors were missing QPDF_DLL, which could cause some
Windows applications to fail to link.

Give objects descriptions and context so it is possible to issue
warnings instead of fatal errors for attempts to access objects of the
wrong type.

The Apache License version 2.0 is now the primary license for qpdf.
However, users may, at their option, continue to use Artistic version
2.0.