doc: updated fs #5862 removed irrelevant data in fs.markdown

fs.readFile, fs.writeFile and fs.appendFile doc changes
pulled back from master included details not relevant to
v4.

PR-URL: #5877
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/fs.markdown

@@ -252,7 +252,7 @@ fail, and does nothing otherwise.
 
 ## fs.appendFile(file, data[, options], callback)
 
-* `file` {String|Number} filename or file descriptor
+* `file` {String} filename
 * `data` {String|Buffer}
 * `options` {Object|String}
   * `encoding` {String|Null} default = `'utf8'`
@@ -278,10 +278,6 @@ If `options` is a string, then it specifies the encoding. Example:
 fs.appendFile('message.txt', 'data to append', 'utf8', callback);
 ```
 
-Any specified file descriptor has to have been opened for appending.
-
-_Note: Specified file descriptors will not be closed automatically._
-
 ## fs.appendFileSync(file, data[, options])
 
 The synchronous version of [`fs.appendFile()`][]. Returns `undefined`.
@@ -620,7 +616,7 @@ Synchronous readdir(3). Returns an array of filenames excluding `'.'` and
 
 ## fs.readFile(file[, options], callback)
 
-* `file` {String | Integer} filename or file descriptor
+* `file` {String} filename
 * `options` {Object | String}
   * `encoding` {String | Null} default = `null`
   * `flag` {String} default = `'r'`
@@ -646,10 +642,6 @@ If `options` is a string, then it specifies the encoding. Example:
 fs.readFile('/etc/passwd', 'utf8', callback);
 ```
 
-Any specified file descriptor has to support reading.
-
-_Note: Specified file descriptors will not be closed automatically._
-
 ## fs.readFileSync(file[, options])
 
 Synchronous version of [`fs.readFile`][]. Returns the contents of the `file`.
@@ -945,7 +937,7 @@ the end of the file.
 
 ## fs.writeFile(file, data[, options], callback)
 
-* `file` {String | Integer} filename or file descriptor
+* `file` {String} filename
 * `data` {String | Buffer}
 * `options` {Object | String}
   * `encoding` {String | Null} default = `'utf8'`
@@ -974,14 +966,10 @@ If `options` is a string, then it specifies the encoding. Example:
 fs.writeFile('message.txt', 'Hello Node.js', 'utf8', callback);
 ```
 
-Any specified file descriptor has to support writing.
-
 Note that it is unsafe to use `fs.writeFile` multiple times on the same file
 without waiting for the callback. For this scenario,
 `fs.createWriteStream` is strongly recommended.
 
-_Note: Specified file descriptors will not be closed automatically._
-
 ## fs.writeFileSync(file, data[, options])
 
 The synchronous version of [`fs.writeFile()`][]. Returns `undefined`.