passing large data between marxan and r is slow

[jeffreyhanson]

have r preallocate arrays, and then have marxan populate them with results, this avoid issues with sending large amounts of data to and from marxan, and also we can avoid using Rcpp data structure or Rcpp data structures and stick with C. this will facilitate the marxan interoperating with other non-R systems, eg. idrisi, qmarxan, arcgis, qgis, cluz