work around the missing (gtar) -T (--files-from) option of our paxtar

work around the missing (gtar) -T (--files-from) option of our paxtar
in pkg_create so that it should work now with paxtar (the -X option is
still missing due to missing -X - in the gtar meaning --exclude-from-file
option)

i did it by changing the FreeBSD way of doing it (open a pipe to tar with
-T - (read filenames from stdin) and give all the filenames to the pipe)
to constructing a big :-) argumentlist for tar and executing it without
the pipe (not the best solution but it works :-)