RFR: 8263080: Obsolete relationship in MulticastSocket API documentation. [v4]

[Daniel Fuchs]

> Now that DatagramSocket has been updated by JDK-8237352 to support joining multicast group, this sentence in the API class level documentation of MulticastSocket is obsolete and should be removed:
> 
> "A MulticastSocket is a (UDP) DatagramSocket, with additional capabilities for
>  joining "groups" of other multicast hosts on the internet." 
>  
>  Not sure whether this requires a CSR. I guess not?

Daniel Fuchs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Merge branch 'master' into ms-doc-8263080
 - Incorporated CSR review feedback
 - Merge branch 'master' into ms-doc-8263080
 - Added suggested text. Fixed example code.
 - Improved first sentence
 - 8263080: Obsolete relationship in MulticastSocket API documentation.

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2842/files
  - new: https://git.openjdk.java.net/jdk/pull/2842/files/13b55f44..21bf729d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2842&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2842&range=02-03

  Stats: 35385 lines in 1550 files changed: 27048 ins; 4110 del; 4227 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2842.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2842/head:pull/2842

PR: https://git.openjdk.java.net/jdk/pull/2842