Port the contents of https://bugs.openjdk.org/browse/JDK-8376274 over, and utilize the enhanced tag to link to the preview JLS/JVMS changeset directly from the API specs.
The `JSpec` and `ExactConversionsSupport` changes are identical to mainline. The rest are valhalla-specific fixes. ------------- Commit messages: - Fix preview spec broken links - 8376274: JSpec preview support and output enhancement Changes: https://git.openjdk.org/valhalla/pull/1988/files Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1988&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8375777 Stats: 81 lines in 10 files changed: 49 ins; 6 del; 26 mod Patch: https://git.openjdk.org/valhalla/pull/1988.diff Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1988/head:pull/1988 PR: https://git.openjdk.org/valhalla/pull/1988
