RFR: 8269429: Linux: Only the last APPLICATION_MODAL window behaves corretly

Tue Jun 29 12:16:16 UTC 2021

The PR approach is to set  `gtk_window_set_keep_above` to true on APPLICATION_MODAL windows, so they will not stay behind non APPLICATION_MODAL windows.

This is passed on WindowStage.java:198 as a mask.

The weird thing is that `_enterModal()` is never called. This seems the right function to be called for `APPLICATION_MODAL`, as `_enterModalWithWindow` fits for `WINDOW_MODAL`.

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Commit messages:
 - Only if not WINDOW_MODAL
 - Fix for JDK-8210973
 - Merge branch 'openjdk:master' into master
 - Merge pull request #18 from openjdk/master
 - Merge pull request #17 from openjdk/master
 - Merge pull request #16 from openjdk/master
 - Merge pull request #15 from openjdk/master
 - Merge pull request #14 from openjdk/master
 - Merge pull request #13 from openjdk/master
 - Merge pull request #12 from openjdk/master
 - ... and 8 more: https://git.openjdk.java.net/jfx/compare/78179be1...7b483449

Changes: https://git.openjdk.java.net/jfx/pull/551/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=551&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269429
  Stats: 14 lines in 3 files changed: 10 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jfx/pull/551.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/551/head:pull/551

PR: https://git.openjdk.java.net/jfx/pull/551