json-module: doc update
json-module uses Bstrings for arrays to speed up json_generate

(Bstrings were optimized for concatenation in commit 264c638def48854c133a1a66ddb0d928cbb4e2c2.)
json-module uses Bstrings only internally to speed up json_generate
Performance enhancements to the json_generate.

_json_generate_string modified to use table lookups, and now returns a BString_Type object.

Integrated json-module.inc into json-module.c.

json.sl; Replaced the switch statements by function pointers.
pre2.3.0-92: Added bstrjoin and bstrcat intrinsics.
pre2.3.0 change 93: Modified the json module to use bstrcat.  Name changes: json_generate/parse -> json_encode/decode.