bsdtar needed for libsigc++ extraction

["Jeremy C. Reed" <reed%reedmedia.net@localhost>]

devel/libsigc++/Makefile has:

1.26         (wiz      21-Sep-07): # use something that can extract long 
filenames in GNU format on NetBSD 1.6.x
1.29         (joerg    25-May-08): EXTRACT_USING=               bsdtar

If that is for NetBSD 1.6.x then maybe it should check for that?

Or adjust comment if we don't have any way to know what tar is good 
enough so always use bsdtar?

But if I use newer NetBSD, I assume my tar is good enough so maybe bsdtar 
shouldn't be needed.

I commented out that and it looks like my tar is good enough.