Function xmlAddEntity 

pub unsafe extern "C" fn xmlAddEntity(
    doc: *mut xmlDoc,
    extSubset: c_int,
    name: *const xmlChar,
    type_: c_int,
    publicId: *const xmlChar,
    systemId: *const xmlChar,
    content: *const xmlChar,
    out: *mut *mut xmlEntity,
) -> c_int