Add libxml2-devel to requirements in HACKING
Add libxml2-devel to requirements in HACKING

raphink/augeas,ptoscano/augeas,jasperla/augeas,domcleal/augeas,kumy/augeas,dafugg/augeas,dafugg/augeas,jjlin/augeas,domcleal/augeas,jjlin/augeas,kumy/augeas,ptoscano/augeas,hercules-team/augeas,lutter/augeas,pevalme/augeas,jjlin/augeas,hercules-team/augeas-do-not-use,GeoffWilliams/augeas,dafugg/augeas,jtopjian/augeas,manandbytes/augeas,kunkku/augeas,hercules-team/augeas-do-not-use,lutter/augeas,mlichvar/augeas,GeoffWilliams/augeas,pevalme/augeas,pevalme/augeas,kunkku/augeas,ptoscano/augeas,mlichvar/augeas,kunkku/augeas,manandbytes/augeas,jasperla/augeas,hercules-team/augeas-do-not-use,mlichvar/augeas,raphink/augeas,kumy/augeas,MikaelSmith/augeas,MikaelSmith/augeas,kumy/augeas,hercules-team/augeas,lutter/augeas,mchf/augeas,domcleal/augeas,mchf/augeas,jtopjian/augeas