[jfx11u] RFR: 8278980: Update WebKit to 613.1

[Kevin Rushforth]

Nearly clean backport to `jfx11u` (the only conflict was in the copyright years in one of the unit tests). I tested this along with the other VS 2019 and WebKit 613.1 fixes together in the `test-kcr-11.0.15` branch.

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Commit messages:
 - 8278980: Update WebKit to 613.1

Changes: https://git.openjdk.java.net/jfx11u/pull/77/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=77&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278980
  Stats: 412962 lines in 6737 files changed: 231442 ins; 135635 del; 45885 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/77.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/77/head:pull/77

PR: https://git.openjdk.java.net/jfx11u/pull/77