configure.ac: add docbook-to-man to dbparsers
configure.ac: add docbook-to-man to dbparsers

Debian and Ubuntu uses docbook2x-man, but some other distr like suse
uses docbook-to-man. I think all of them should work on LXC.

Signed-off-by: Qiang Huang <488e06933c295c76472a67dbc6657ac40a756953@huawei.com>
Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

armcc/lxc,GreatFruitOmsk/lxc,aeris/lxc,terceiro/lxc,lisongmin/lxc,Ponce/lxc,hkjolhede/lxc,raspberrypython/lxc,GreatFruitOmsk/lxc,tych0/lxc,ss1h2a3tw/lxc,regit/lxc,rldleblanc/lxc,federicobriata/lxc,ojkastl/lxc_Patches,Distrotech/lxc,Distrotech/lxc,thmo/lxc,yubo/lxc,ojkastl/lxc_Patches,akshaykarle/lxc,jirislaby/lxc,lisongmin/lxc,raspberrypython/lxc,thmo/lxc,szaszg/lxc,hallyn/lxc,federicobriata/lxc,aeris/lxc,armcc/lxc,ioops/lxc,sapun/lxc,sapun/lxc,rowhit/lxc,yubo/lxc,codebauss/lxc,hallyn/lxc,bmoar/lxc,bmoar/lxc,ojkastl/lxc_Patches,armcc/lxc,ss1h2a3tw/lxc,lazy404/lxc,ksperis/lxc,caglar10ur/lxc,lazy404/lxc,terceiro/lxc,terceiro/lxc,hfuCN/lxc,christiaan/lxc,ysbnim/lxc,LynxChaus/lxc,jirislaby/lxc,Pelagicore/lxc,hkjolhede/lxc,Ponce/lxc,rldleblanc/lxc,weizhenwei/lxc,JohnPeacockMessageSystems/lxc,ojkastl/lxc_Patches,jirislaby/lxc,weizhenwei/lxc,fwilson42/lxc,yubo/lxc,ysbnim/lxc,Distrotech/lxc,bostjan/lxc,ecarrara/lxc,bostjan/lxc,JohnPeacockMessageSystems/lxc,raspberrypython/lxc,codebauss/lxc,bostjan/lxc,federicobriata/lxc,ecarrara/lxc,major/lxc,ecarrara/lxc,weizhenwei/lxc,virajs/lxc,regit/lxc,szaszg/lxc,efiop/lxc,bmoar/lxc,DarknessBeforeDawn/lxc,QingweiPeterLan/cs188-lxc,akshaykarle/lxc,cjwatson/lxc,sapun/lxc,major/lxc,LynxChaus/lxc,QingweiPeterLan/cs188-lxc,virajs/lxc,Ponce/lxc,major/lxc,ksperis/lxc,fwilson42/lxc,caglar10ur/lxc,aeris/lxc,lazy404/lxc,efiop/lxc,GreatFruitOmsk/lxc,szaszg/lxc,ioops/lxc,christiaan/lxc,caglar10ur/lxc,hfuCN/lxc,DarknessBeforeDawn/lxc,ss1h2a3tw/lxc,regit/lxc,cjwatson/lxc,lisongmin/lxc,QingweiPeterLan/cs188-lxc,efiop/lxc,LynxChaus/lxc,tych0/lxc,cjwatson/lxc,rowhit/lxc,JohnPeacockMessageSystems/lxc,Pelagicore/lxc,christiaan/lxc,ksperis/lxc,hkjolhede/lxc,rowhit/lxc,DarknessBeforeDawn/lxc,rldleblanc/lxc,tych0/lxc,thmo/lxc,ioops/lxc,ysbnim/lxc,hfuCN/lxc,virajs/lxc,fwilson42/lxc,hallyn/lxc,codebauss/lxc,akshaykarle/lxc,Pelagicore/lxc