rust-dirstatemap: add `set_tracked` method
This is the new dirstate API that has already been moved to in Python.
It will be used in place of the old `addfile`/`removefile` one.
Differential Revision: https://phab.mercurial-scm.org/D12495
#include <Python.h>
#if PY_MAJOR_VERSION >= 3
#define PYCODETYPE PyObject
#else
#define PYCODETYPE PyCodeObject
#endif
namespace contrib
{
void initpy(const char *cselfpath);
PyObject *pyglobals();
} /* namespace contrib */