Updating converters/p5-JSON from 2.17 to 2.21

Upstream changes:
2.21  Mon Apr  5 14:56:52 2010
[JSON]
- enhanced 'HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER'
- renamed eg/bench_pp_xs.pl to eg/bench_decode.pl
- added eg/bench_encode.pl

2.20  Fri Apr  2 12:50:08 2010
[JSON]
- added eg/bench_pp_xs.pl for benchmark sample
- updated 'INCREMENTAL PARSING' section
[JSON::PP]
- decode_prefix() didn't count a consumed text length properly.
- enhanced XS compatibilty
    in the case of decoding a white space garbaged text.

2.19  Tue Mar 30 13:40:24 2010
[JSON]
- fixed typo (rt#53535 by Angel Abad)
- added a recommendation
              refering to (en|de)code_json to pod (suggested by tokuhirom)
- added 'HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER' to pod.

2.18  Tue Mar 23 15:18:10 2010
[JSON]
- updated document (compatible with JSON::XS 2.29)
[JSON::PP]
- fixed encode an overloaded 'eq' object bug (reported by Alexey A. Kiritchun)
- enhanced an error message compatible to JSON::XS

(sno)