RFR: 8087370: Fix false detection of multitouch events with some touch controllers

[Fabian Wolter]

This fixes JDK-8087370.

There are sometimes multitouch events detected, when only a single touch should be detected under certain conditions. This lead to touch events on previous touch positions.

The referenced bug is closed with "won't fix" with the justification it would be platform specific. But this is not correct. It affects all Linux platforms combined with a touch controller, which sends the touch events in an uncommon, but valid(!), order.

We encountered this problem with the touch controller ILI2511 with firmware V6000_V1 in the Tianma display TM070JVHG33. This patch fixes the problem. It is the same patch attached to above bug report.

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Commit messages:
 - 8087370: Fix false detection of multitouch events with some touch controllers

Changes: https://git.openjdk.java.net/jfx/pull/641/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=641&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8087370
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/641.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/641/head:pull/641

PR: https://git.openjdk.java.net/jfx/pull/641