RFR: JDK-8267204: Expose access to underlying streams in Reporter [v3]

[Jonathan Gibbons]

> Please review an update to `jdk.javadoc/jdk.javadoc.doclets.Reporter` to add 3 new methods and to improve the descriptions of other parts of the interface.
> 
> The new methods provide access to the underlying streams (informally, for standard output and diagnostic output), and a new `report` method to report diagnostics at an arbitrary position in a file being read by a doclet, or a taglet within a doclet.

Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  use printRawLines instead of println for correct newline handline on Windows
  address review feedback

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4216/files
  - new: https://git.openjdk.java.net/jdk/pull/4216/files/78e811b1..1b70b66d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4216&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4216&range=01-02

  Stats: 7 lines in 3 files changed: 0 ins; 2 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4216.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4216/head:pull/4216

PR: https://git.openjdk.java.net/jdk/pull/4216