RFR: JDK-8279636: Update JCov version to 3.0.12

[Alexandre Iline]

JDK-8279636: Update JCov version to 3.0.12

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Commit messages:
 - JDK-8279636: Update JCov version to 3.0.12

Changes: https://git.openjdk.java.net/jdk/pull/7218/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7218&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279636
  Stats: 8 lines in 1 file changed: 0 ins; 7 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7218.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7218/head:pull/7218

PR: https://git.openjdk.java.net/jdk/pull/7218