Fix error and waring in make doc
#4370 causes an error of checking the depth of heading level in buffer api doc during make doc as
/home/ohtsu/github/node/tools/doc/generate.js:52
if (er) throw er;
^
Error: Inappropriate heading level
{"type":"heading","depth":3,"text":"Buffers and Character Encodings"}
at /home/ohtsu/github/node/tools/doc/html.js:192:17
at Array.forEach (native)
at buildToc (/home/ohtsu/github/node/tools/doc/html.js:189:9)
at render (/home/ohtsu/github/node/tools/doc/html.js:71:3)
at /home/ohtsu/github/node/tools/doc/html.js:37:7
at tryToString (fs.js:414:3)
at FSReqWrap.readFileAfterClose [as oncomplete] (fs.js:401:12)
make: *** [out/doc/api/all.html] Error 1
This just changes error headings of the sections to the 2nd level.
And I also found that warning was shown from json.js as
Warning: invalid param "end]"
> {"textRaw":"`end` Number, Optional, Default: `buffer.length` ","name":"end","desc":"Number, Optional, Default: `buffer.length`"}
> buf.slice([start[, end]])
This is due to insufficient trimming of right square brackets and it is fixed.
R= @jasnell