doc: fix fs.read arg type and setImmediate desc

[darai0512]

Checklist

• documentation is changed or added
• commit message follows [commit guidelines][]

Affected core subsystem(s)

doc

Description of change

About fs.read's 2nd argument, I think string is invalid.
https://github.com/nodejs/node/blob/v6.x-staging/src/node_file.cc#L1247-L1248

$cat fs_invalid_read_arg.js
const fs = require('fs');
fs.open('./fs_invalid_read_arg.js', 'r', (err, fd) => {
  const buffer = ''; // About 2nd argument, string is error. Buffer.alloc(1024) is ok.
  fs.read(fd, buffer, 0, 1024, 0, (err, byteRead, buffer) => {
    console.log('ok');
  })
});

$node fs_invalid_read_arg.js
fs.js:129
    throw new Error('Unknown encoding: ' + encoding);
    ^

Error: Unknown encoding: 1048576
    at assertEncoding (fs.js:129:11)
    at Object.fs.read (fs.js:654:5)
    at fs.open (/Users/daiki/workspace/fs_invalid_read_arg.js:5:6)
    at FSReqWrap.oncomplete (fs.js:123:15)

And also, about setImmediate, the timing of the execution is after timers in Event Loop of over v0.9, though it is correct in Event Loop under v0.8.
So, I deleted the description because the timing depended on Nodejs version.

[vsemozhetbyt]

I may be wrong, but is it worth to be split into separate commits or even PRs?

[darai0512]

@vsemozhetbyt
Sure, I will divide my commit into two commits.

[darai0512]

@vsemozhetbyt
I divided it. PTAL.

[jasnell]

@Fishrock... are you good with the Timers doc change here?

[addaleax]

^^^ That ping should probably have gone to @Fishrock123 ;)

[jasnell]

Landed in 0844262...e9f2ec4

[MylesBorins]

is this accurate for v6.x?

[gibfahn]

is this accurate for v6.x?

ping

[darai0512]

@MylesBorins @gibfahn
Sorry for my late reply.
I think so, these are accurate for v6.x.