RFR: 8276173: Clean up and remove unneeded casts in HeapDumper [v2]

[Leo Korinth]

On Tue, 2 Nov 2021 19:25:40 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> HeapDumper does a lot of unneeded casts. Some arguments should be const. Headers are not correctly sorted. Comment about identifier size on Windows and Solaris is not true.
>> 
>> First I cleaned up casting in the "union casting", but then I decided it was better to create a temporary bit_cast that we can use until we get the proper one in c++20.
>
> Leo Korinth has updated the pull request incrementally with one additional commit since the last revision:
> 
>   restart failed github tests

Thanks Coleen and Harold!

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PR: https://git.openjdk.java.net/jdk/pull/6211