OpenSystemsDevelopment / qpdf

Since g++ (as of this writing) uses c++14 by default, this prevents me
from accidentally using c++14 features.

This covers up forgetting to use QPDF_DLL and QPDF_DLL_CLASS.

Clang seems to be slightly stricter than gcc.

Have classes contain only a single private member of type
PointerHolder<Members>. This makes it safe to change the structure of
the Members class without breaking binary compatibility. Many of the
classes already follow this pattern quite successfully. This brings in
the rest of the class that are part of the public API.

Based on sizeof(size_t). Assumes 64 if not 32.

Since autogenerated files are now committed, we no longer need to
rerun ./autogen.sh and actually shouldn't because it could mask
errors.