Fixed compiler warnings in the c++ build

[MatthewHartley]

Proposed changes

When I was building this in my gentoo system, I was bombarded with compiler warnings that looked scary at first glance. This removes these warnings so that installs look less chaotic. One group of warnings was complaining that the order in which == operators were declared was undefined, so making all four equals/not equals operations in the value_ref class depend on a single function was fragile. To fix this, I implemented all 4 explicitly using the equal_to function. The other is another that enums need to be explicitly static_casted since direct adding between two different enum types is deprecated, now the only warning is about calling free on a heap object in a yyparse function, which from a cursory glance is the compiler not realizing that it only gets freed if it isn't a heap object

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Documentation content changes
• Other (please describe):

Checklist

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• I added tests that prove my fix is effective or that my feature works
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