RFR: 8327995: Remove unused Unused_Variable

[Kim Barrett]

On Tue, 12 Mar 2024 16:13:02 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> This code in `globalDefinitions.hpp` is unused and should be removed:
> 
> 
> //----------------------------------------------------------------------------------------------------
> // Utility macros for compilers
> // used to silence compiler warnings
> 
> #define Unused_Variable(var) var

Looks good, and trivial.

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Marked as reviewed by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18242#pullrequestreview-1931546798