RFR: 8312121: Fix -Wconversion warnings in tribool.hpp [v4]

[David Holmes]

On Tue, 25 Jul 2023 15:16:06 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Assigning _value first, and then doing _value | 2 doesn't get -Wconversion warnings.  Also, reduced include file inclusion a little.
>> Tested with tier1 on linux-x64-debug, windows-x64-debug, macos-aarch64-debug
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add some more u1 casts to keep Windows compiler happy hopefully.

To me the fact we have so much trouble placating the compilers suggests that we are doing something wrong/broken here!  :(

Is the `& 3` still needed with the extra u1 cast? I'm gonna guess yes as a u1 doesn't fit in a uchar:2 any better than a uint does.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14892#pullrequestreview-1546780415