OpenSystemsDevelopment / qpdf

When seeing to a position based on a value read from the input, we are
prone to integer overflow (fuzz issue 15442). Seek in two stages to
move the overflow check into the input source code.

This makes it faster to iterate on the other ones.

Per user suggestion in issue 351.

This covers up forgetting to use QPDF_DLL and QPDF_DLL_CLASS.

Just because we know an indirect reference is null, doesn't mean we
shouldn't keep it indirect.

For some reason, qpdf from the beginning was replacing indirect
references to null with literal null in arrays even after removing the
old behavior of flattening scalar references. This seems like a bad
idea.

This message used to only appear for PDF >= 1.2. The invalid name is
valid for PDF 1.0 and 1.1. However, since QPDFWriter may write a newer
version, it's better to detect and warn in all cases. Therefore make
the warning more informative.

This change works around STL problems with Embarcadero C++ Builder
version 10.2, but std::vector is more common than std::list in qpdf,
and this is a relatively new API, so an API change is tolerable.

Thanks to Thorsten Schöning <6223655+ams-tschoening@users.noreply.github.com>
for the fix.

There were a few cases that could be caused by invalid input rather
than bugs in the code which were throwing logic_error instead of
runtime_error.