spcdns: expose print / debug functions to client applications

I needed some debugging functions when using `SPCDNS` inside my own up-and-coming open-source application. However I noticed that the debug functions were hidden and couldn't be accessed by other parties. So I moved them to a separate `.o`, exposed them, and updated the `README` to show how to run the UT's, and include a Contributors section (since this is the standard practice to keep licenses straight).

Below I include the proof that everything still works, and the functions appear where you'd expect them to be:

    $ nm built/libspcdns.a  | fgrep -i print
                    U sprintf
    000000000000025c T dns_print_answer
    000000000000008e T dns_print_header
    0000000000000169 T dns_print_question
    0000000000000000 T dns_print_result
                    U fprintf
                    U printf
    $ nm built/libspcdns.so  | fgrep -i print
    0000000000006d1b T dns_print_answer
    0000000000006b2b T dns_print_header
    0000000000006c18 T dns_print_question
    0000000000006a95 T dns_print_result
                    U fprintf@@GLIBC_2.2.5
                    U printf@@GLIBC_2.2.5
                    U sprintf@@GLIBC_2.2.5
    $ built/dotest -d -s 8.8.8.8 www.google.com.
    OUTGOING:

    ... MEMORY DUMP ...

    INCOMING:

    ... MEMORY DUMP ...

    Bytes used: 680

    ; Questions            = 1
    ; Answers              = 5
    ; Name Servers         = 0
    ; Additional Records   = 0
    ; Authoritative Result = false
    ; Truncated Result     = false
    ; Recursion Desired    = true
    ; Recursion Available  = true
    ; Result               = No error

    ;;; QUESTIONS

    ;www.google.com. IN A

    ;;; ANSWERS

    www.google.com.           206   IN      A       74.125.239.148
    www.google.com.           206   IN      A       74.125.239.145
    www.google.com.           206   IN      A       74.125.239.144
    www.google.com.           206   IN      A       74.125.239.147
    www.google.com.           206   IN      A       74.125.239.146

    ;;; NAMESERVERS


    ;;; ADDITIONAL