OpenSystemsDevelopment / qpdf

JSON accepts scientific notation, but PDF doesn't.

Change default for SF_FlateLzwDecode::columns to 1

Reduce copying of Buffer contents

Also, don't search for /Contents name unless the result is used.

Also, fix test cases.

The new method is temporarily an (almost) complete copy of parse, which is
temporarily (almost) unchanged.

Fixes #864. QPDFTokenizer::getValue originally had a std::string_view
return type, which was changed to std::string without removing some
unnecessary string creation.