fix stdint import to build on g++13

[MRandl]

• [yes] Does this PR have a descriptive title that could go in our release notes?
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• [no] Does this PR modify any existing APIs?
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Reference Issues

Fixes #570

What does this implement/fix? Briefly explain your changes.

ann_exception.h contained a reference to the type uint32_t, which is imported implicitly by g++9 but not g++13, resulting in build failure.
We patch this by explicitly including stdint.h (and not cstdint, to avoid changing the namespace in the signatures, upon which some people might depend)

[MRandl]

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