RFR: 8320965: Scrolling on a touch enabled display fails on Wayland [v3]

[Jose Pereda]

> This PR replaces the deprecated `gdk_pointer_grab` with `gdk_seat_grab`, and `gdk_pointer_ungrab ` with `gdk_seat_ungrab`, using runtime checks and wrapped functions for GTK 3.20+ (so systems without it still run with GTK 3.8+), and fixes the dragging issue on Wayland.

Jose Pereda has updated the pull request incrementally with one additional commit since the last revision:

  Add compile-time checks to GdkSeat

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1305/files
  - new: https://git.openjdk.org/jfx/pull/1305/files/99230ca6..f8ffe87f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1305&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1305&range=01-02

  Stats: 8 lines in 1 file changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1305.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1305/head:pull/1305

PR: https://git.openjdk.org/jfx/pull/1305