Use newer plibc, adjust the code as needed

Use plibc_set_stat_size_size
Use plibc_set_stat_time_size
Update plibc header
Check for _stati64 (needed due to the new plibc header)

git-svn-id: https://gnunet.org/svn/gnunet@31676 140774ce-b5e7-0310-ab8b-a85725594a96
Fix gnunet-config check in gnunet-gns-import, don't add records twice

git-svn-id: https://gnunet.org/svn/gnunet@31677 140774ce-b5e7-0310-ab8b-a85725594a96