Enforce synchronized documentation

$ autoreconf -fi && ./configure --enable-maintainer-mode && make maintainer-clean && autoreconf -fi && ./configure --enable-maintainer-mode && make -j12 all
...
making all in /root/bind9/doc
make[1]: Entering directory '/root/bind9/doc'
making all in /root/bind9/doc/man
make[2]: Entering directory '/root/bind9/doc/man'
for man in arpaname.1in ddns-confgen.8in delv.1in dig.1in dnssec-cds.8in dnssec-checkds.8in dnssec-coverage.8in dnssec-dsfromkey.8in dnssec-importkey.8in dnssec-keyfromlabel.8in dnssec-keygen.8in dnssec-keymgr.8in dnssec-revoke.8in dnssec-settime.8in dnssec-signzone.8in dnssec-verify.8in dnstap-read.1in filter-aaaa.8in host.1in mdig.1in named-checkconf.8in named-checkzone.8in named-journalprint.8in named-nzd2nzf.8in named-rrchecker.1in named.conf.5in named.8in nsec3hash.8in nslookup.1in nsupdate.1in rndc-confgen.8in rndc.conf.5in rndc.8in pkcs11-destroy.8in pkcs11-keygen.8in pkcs11-list.8in pkcs11-tokens.8in; do \
  [ -e "$man" ] || cp -f ./"$man" .; \
done
cp: cannot stat './arpaname.1in': No such file or directory
cp: cannot stat './ddns-confgen.8in': No such file or directory
...
cp: cannot stat './pkcs11-tokens.8in': No such file or directory
make[2]: *** [Makefile:572: ootsetup] Error 1
make[2]: Leaving directory '/root/bind9/doc/man'
make[1]: *** [Makefile:84: subdirs] Error 1
make[1]: Leaving directory '/root/bind9/doc'
make: *** [Makefile:89: subdirs] Error 1

make maintainer-clean removes doc/man/*.1 so ootsetup can't find them and $(MANPAGES_IN) needs to be considered first.