OpenSystemsDevelopment / qpdf

Character transcoding from Unicode to single-byte characters used
hard-coded switch statements because the code predated our adoption of
C++11. Now we have thread-safe, static initialization of map literals,
so use that instead.

I was using AttributeMacros incorrectly, and a recent update to
clang-format broke the formatting.

Remove the name/number tree object helper constructors that don't take
a QPDF&.

* Merge overloaded functions by adding default values
* Remove non-const methods that are identical to const methods

This enables RTTI so we can use dynamic_cast on them across the shared
object boundary.

* Change DLL_EXPORT to libqpdf_EXPORTS (internal to the build). The
  new name is cmake's default, is more conventional, and is less
  likely to clash with other symbols.
* Add QPDF_DLL_PRIVATE for non-Windows
* Make logic around when to define QPDF_DLL et al more explicit
* Add detailed comments

Prior to the cmake conversion, several private classes had methods
that were exported into the shared library so they could be tested
with libtests. With cmake, we build libtests using an object library,
so this is no longer necessary. The methods that are disappearing from
the ABI were never exposed through public headers, so no code should
be using them. Removal had to wait until the window for ABI-breaking
changes was open.

Increase to POINTERHOLDER_TRANSITION=4

Increase to POINTERHOLDER_TRANSITION=3

patrepl s/PointerHolder/std::shared_ptr/g **/*.cc **/*.hh
patrepl s/make_pointer_holder/std::make_shared/g **/*.cc
patrepl s/make_array_pointer_holder/QUtil::make_shared_array/g **/*.cc
patrepl s,qpdf/std::shared_ptr,qpdf/PointerHolder, **/*.cc **/*.hh
git restore include/qpdf/PointerHolder.hh
git restore libtests/pointer_holder.cc
cleanpatch
./format-code

(patrepl and cleanpatch are my own utilities)

patrepl s/PointerHolder/std::shared_ptr/g {include,libqpdf}/qpdf/*.hh
patrepl s/PointerHolder/std::shared_ptr/g libqpdf/*.cc
patrepl s/make_pointer_holder/std::make_shared/g libqpdf/*.cc
patrepl s/make_array_pointer_holder/QUtil::make_shared_array/g libqpdf/*.cc
patrepl s,qpdf/std::shared_ptr,qpdf/PointerHolder, **/*.cc **/*.hh
git restore include/qpdf/PointerHolder.hh
cleanpatch
./format-code

Add comments to force line breaks, parenthesize function arguments
that are contatenated strings, etc. -- these kinds of changes improve
clang-format's results and also cause emacs cc-mode to match
clang-format. After this type of change, most of the time, when
clang-format and emacs disagree, clang-format is better.

Run this:

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