Problem: Can't handle two messages right after each other.
Solution: Find the end of the JSON. Read more when incomplete. Add a C
test for the JSON decoding.
Problem: Can't encode a Funcref into JSON. jsonencode() doesn't handle the
same list or dict twice properly. (Nikolay Pavlov)
Solution: Give an error. Reset copyID when the list or dict is finished.
Problem: No tests for comparing special variables. Error in jsondecode()
not reported. test_json does not work Japanse system.
Solution: Set scriptencoding. (Ken Takata) Add a few more tests. Add error.
