[roots_mod.c] new r-th root code for any r (untested, but unused so far...)
[roots_mod.c] new r-th root code for any r (untested, but unused so far...)

mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs