RFR: 8273743: KeyCharacterCombination for "+" does not work on US QWERTY keyboard layout [v3]

[Martin Fox]

> There was a mismatch between the way `get_glass_key` generated the Java key code for a given key press and how `getKeyCodeForChar` determined the key code for the matching character. For example, when pressing the plus sign on a US keyboard `get_glass_key` correctly generated `KeyCode.EQUALS` but `getKeyCodeForChar("+")` generated `KeyCode.PLUS`.
> 
> In this PR `getKeyCodeForChar` mirrors the behavior of `get_glass_key`; it determines which key the character lies on and generates a key code based on the unshifted character on  the same key.
> 
> I'm working on a more comprehensive test case that allows you to press any key on the keyboard and test whether a KeyCharacterCombination for that character will succeed or not. I've attached it to this thread. It might be worth submitting as a manual test case
> [CharComboTest.txt](https://github.com/openjdk/jfx/files/7247265/CharComboTest.txt)
> .

Martin Fox has updated the pull request incrementally with one additional commit since the last revision:

  Remove extraneous whitespace

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/635/files
  - new: https://git.openjdk.java.net/jfx/pull/635/files/2e8510bf..69d46c2e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=635&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=635&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/635.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/635/head:pull/635

PR: https://git.openjdk.java.net/jfx/pull/635