C interface: documenting how to get results from Pl_Query_Call() and Pl_Query_Next_Solution()

[Ricky Husky]

Dear GNU Prolog developers,

 1.The C interface has Pl_Rd_String (it exist in code but is not documented).

 2. It feels a little inconvenient in having to parse ASCII output of Pl_Rd_String back to binary in C code that consumes the Prolog output.

And it will greatly help, like other Prolog implementations, to have a interface to the Prolog internal data structures, presenting output in "in-memory binary format" of outputs.

Like an array of pointers to GNUProlog data type (struct) objects.

Thank you very much,

Ricky