Update p5-JSON to 2.12.

2.12  Wed Jul 16 11:14:35 2008
[JSON]
- made compatible with JSON::XS 2.22

[JSON::PP]
- fixed the incremental parser in negative nest level
    (pointed and patched by Yuval Kogman)

2.11  Tue Jun 17 14:30:01 2008
[JSON::PP]
- fixed the decoding process which checks number.
    regarded number like chars in Unicode (ex. U+FF11) as [\d].
- enhanced error messages compatible to JSON::XS.

(obache)