RFR: 8243208: Clean up JVMFlag implementation [v6]

[David Holmes]

On Thu, 10 Sep 2020 04:36:51 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> The initial commit [d85cbd6](https://github.com/openjdk/jdk/commit/d85cbd638f5b87c80eee9a92d10e1ac19d9bb2f8) is the
>> same patch as
>> [8243208-cleanup-jvmflag-impl.v02](https://cr.openjdk.java.net/~iklam/jdk16/8243208-cleanup-jvmflag-impl.v02/)
>> published in
>> [hotspot-dev at openjdk.java.net](https://mail.openjdk.java.net/pipermail/hotspot-dev/2020-September/042863.html).  The
>> rest of the review will continue on GitHub. I will add new commits to respond to comments to the above e-mail.
>
> Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes
> the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last
> revision:
>  - Merge branch 'master' into 8243208-cleanup-jvmflag-impl
>  - Minor code clean up suggested by David Holmes
>  - Feedback by Gerard (hotspot-dev/2020-September/043019.html)
>  - Refactored JVMFlagLookup::hash_code(); Cleaned up LimitGetter::no_limit()
>  - Fixed JVMFlag::is_writeable()
>  - (a) coding style nits and comments, (b) updated HOWTO in globals.hpp, (c) added JVMFlag::check_all_flag_declarations(),
>    (d) removed product_rw which is not used by any flags
>  - 8243208: Clean up JVMFlag implementation

Marked as reviewed by dholmes (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/82