pmacct: Remove autogen.sh step so it builds with autoconf-2.72

pmacct: Remove autogen.sh step so it builds with autoconf-2.72

- Although the pmacct source tarball has a configure script provided, for some reason
   the lfs file ran autogen.sh first and therefore re-created the configure script.
   Whatever the autogen.sh script was creating it ended up with a result that the new
   autoconf-2.72 didn't like. Some problem with an end of line that was not of the
   expected structure.
- It seems reasonable to use the configure script that has been provided by the pmacct
   developers in the source tarbal, so this patch removes the use of the autogen.sh
   script and uses the configure script provided by pmacct. This then allowed a
   successful build with the autoconf-2.72

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>