Fix C++ and Cython io types

[vyasr]

Description

The C++ I/O types were previously not specifying a base type despite the fact that the Cython code was relying on the base being an int32. This has apparently never bitten us before, but in theory this could go very wrong since it leaves the underlying type up to the compiler and if the C++ binary used something other than an int32 that would result in an ABI incompatibility with the Python build that would produce spurious results.

While fixing this, I also noticed that the Cython contained a number of erroneous (likely outdated) declarations. Since Cython extern declarations are simply an indicate to Cython of how to resolve a function call if it appears in compiled Cython code, these were not causing any build failures because these were all unused APIs, so I removed them from the Cython with no further changes needed.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[vyasr]

/merge