OpenSystemsDevelopment / qpdf

If duplicate keys are encountered, overwrite earlier values with the latest
value.

Create a simple utility class for writing JSON to a pipeline.

Using search and replace.

Recognise that JSON objects are effectively shared pointers to JSON_value.

Eliminate the use of shared pointers in JSONParser

Reduce boilerplate and increase efficiency by avoiding setting and
branching on action and ready in getToken.

Also, reject them in strings.

Handle all incomplete token type errors in tokenError.

(except '\\' and '\uXXXX')