fix autogen.sh

fix autogen.sh

Building from source fails on a clean git pull, due to autogen.sh failing.

$ ./autogen.sh
+ make -C man -f Makefile.am infiles
make: Entering directory `/home/amb/nbd/nbd/man'
make: *** No rule to make target `infiles'. Stop.
make: Leaving directory `/home/amb/nbd/nbd/man'

A manual autoreconf does this.

$ autoreconf -f -i -s
configure.ac:123: required file `man/nbd-client.8.sh.in' not found
configure.ac:123: required file `man/nbd-server.5.sh.in' not found
configure.ac:123: required file `man/nbd-server.1.sh.in' not found
autoreconf: automake failed with exit status: 1

I think the attached is the right patch (well, I have ./configure
now). There may be a prettier way of doing it (e.g. putting an
"infiles" target into man/Makefile.am) but this is least intrusive.

--
Alex Bligh

Signed-off-by: Alex Bligh <alex@alex.org.uk>