minor coding style fixes.
updated docs to reflect recent changes.
bugfix: the output buffer size would get wrong when the affected_rows…
… field is larger than a single-digit number. thanks Wendal Chen for reporting this by using clang.
bugfix: fixed a compilation error when DDEBUG=1. thanks 郭颖.
now we only register our filters when rds_json is actually used in ng…
states that we are production ready :)