Evaluate C++ flags type

[gregorgorjanc]

tskit C uses https://tskit.dev/tskit/docs/stable/c-api.html#c.tsk_flags_t

typedef uint32_t tsk_flags_t
Container for bitwise flags.

Bitwise flags are used in tskit as a column type and also as a way to specify options to API functions

When I started I just used int in C++,
but best to be consistent.
What should we use though?
Can we just use tsk_flags_t and how will this interact with R and Rcpp?

[gregorgorjanc]

We do the right thing (pass integer from R to C++ and check that it is not negative and valid for each function call) - I added more validation in #109