ser2net: bump to 2.9

SER2NET_AUTORECONF is needed because of libtool version mismatch.
See error message bellow:

/bin/bash ./libtool --tag=CC   --mode=link gcc -Wall -g -O2   -o
ser2net controller.o dataxfer.o devcfg.o readconfig.o selector.o
ser2net.o utils.o telnet.o buffer.o  -lnsl
libtool: Version mismatch error.  This is libtool 2.4.2
Debian-2.4.2-1ubuntu1, but the
libtool: definition of this LT_INIT comes from libtool 2.2.6b.
libtool: You should recreate aclocal.m4 with macros from libtool 2.4.2
Debian-2.4.2-1ubuntu1
libtool: and run autoconf again.
make: *** [ser2net] Error 63

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>