RFR: 8313424: JavaFX controls in the title bar [v67]

[Michael Strauß]

> Implementation of [`StageStyle.EXTENDED`](https://gist.github.com/mstr2/0befc541ee7297b6db2865cc5e4dbd09).

Michael Strauß has updated the pull request incrementally with two additional commits since the last revision:

 - add MenuBar to stage tester
 - documentation

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1605/files
  - new: https://git.openjdk.org/jfx/pull/1605/files/394a039a..7dc8f5f1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1605&range=66
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1605&range=65-66

  Stats: 27 lines in 2 files changed: 22 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1605.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1605/head:pull/1605

PR: https://git.openjdk.org/jfx/pull/1605