Wrappers for selected functions described at:
http://www.google.com/search?q=gsl_sf_pow_int.h&as_sitesearch=www.gnu.org/software/gsl/manual&btnI=Lucky
wrapper for int gsl_sf_pow_int_e(double x,int n,gsl_sf_result* result);
http://www.google.com/search?q=gsl_sf_pow_int_e&as_sitesearch=www.gnu.org/software/gsl/manual&btnI=Lucky
wrapper for double gsl_sf_pow_int(double x,int n);
http://www.google.com/search?q=gsl_sf_pow_int&as_sitesearch=www.gnu.org/software/gsl/manual&btnI=Lucky