OpenSystemsDevelopment / qpdf

Also remove some shared pointers and use std::string instead of Pl_Buffer
in Pl_QPDFTokenizer.

Remove remaining QPDFTokenizer private methods.
Remove QPDFTokenizer privileged access to Tokenizer.

Add new private Util.hh header to define inline functions and expose as
ordinary functions in QUtil.

Tokens longer than the target cannot be a match and therefore there is no
need to read to the end of token.

Remove unnecessary use of shared pointers and avoid unnecessary string
creation.

For all other token types val and raw_val are identical.

Provide buffered input for QPDFTokenizer.