Modified the FTP server to use the new 'sockfilt' program to do all the socket

level stuff. The FTP server communicates with sockfilt using perl's open2().
This enables easier IPv6 support and hopefully FTP-SSL support in the future.
Added four test cases for FTP-ipv6.

tests/data/test252

@@ -0,0 +1,57 @@
+<info>
+<keywords>
+FTP-ipv6
+EPSV
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data>
+total 20
+drwxr-xr-x   8 98       98           512 Oct 22 13:06 .
+drwxr-xr-x   8 98       98           512 Oct 22 13:06 ..
+drwxr-xr-x   2 98       98           512 May  2  1996 .NeXT
+-r--r--r--   1 0        1             35 Jul 16  1996 README
+lrwxrwxrwx   1 0        1              7 Dec  9  1999 bin -> usr/bin
+dr-xr-xr-x   2 0        1            512 Oct  1  1997 dev
+drwxrwxrwx   2 98       98           512 May 29 16:04 download.html
+dr-xr-xr-x   2 0        1            512 Nov 30  1995 etc
+drwxrwxrwx   2 98       1            512 Oct 30 14:33 pub
+dr-xr-xr-x   5 0        1            512 Oct  1  1997 usr
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+ipv6
+</features>
+<server>
+ftp-ipv6
+</server>
+ <name>
+FTP IPv6 dir list PASV
+ </name>
+ <command>
+-g "ftp://%HOST6IP:%FTP6PORT/"
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+filter off really nothing
+</strip>
+<protocol>
+USER anonymous
+PASS curl_by_daniel@haxx.se
+PWD
+EPSV
+TYPE A
+LIST
+QUIT
+</protocol>
+</verify>