RFR: 8256253: Defer Biased Locking obsoletion to JDK 18

[Patricio Chilano Mateo]

Hi all,

Please review the following change to defer biased-locking obsoletion to 18, as discussed in [1].
I updated the special_jvm_flags table and re-enabled gtest verify_special_flags.

Thanks,
Patricio

[1] https://mail.openjdk.java.net/pipermail/hotspot-dev/2020-November/045454.html

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Commit messages:
 - v1

Changes: https://git.openjdk.java.net/jdk/pull/1281/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1281&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256253
  Stats: 9 lines in 2 files changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1281.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1281/head:pull/1281

PR: https://git.openjdk.java.net/jdk/pull/1281