Fix typo in doc/build-unix.md regarding building without UPnP
Fix typo in doc/build-unix.md regarding building without UPnP

Rebased-From: 947e23d

nigeriacoin/nigeriacoin,coinkeeper/2015-06-22_18-37_dogecoin,marklai9999/Taiwancoin,RazorLove/cloaked-octo-spice,RazorLove/cloaked-octo-spice,Domer85/dogecoin,oklink-dev/bitcoin_block,oklink-dev/bitcoin_block,nsacoin/nsacoin,haisee/dogecoin,koharjidan/dogecoin,Domer85/dogecoin,jarymoth/dogecoin,koharjidan/dogecoin,langerhans/dogecoin,nsacoin/nsacoin,coinkeeper/2015-06-22_18-37_dogecoin,coinwarp/dogecoin,koharjidan/dogecoin,jarymoth/dogecoin,brishtiteveja/sherlockcoin,coinwarp/dogecoin,masterbraz/dg,langerhans/dogecoin,koharjidan/dogecoin,Domer85/dogecoin,RazorLove/cloaked-octo-spice,koharjidan/dogecoin,koharjidan/dogecoin,nsacoin/nsacoin,haisee/dogecoin,Domer85/dogecoin,jarymoth/dogecoin,oklink-dev/bitcoin_block,langerhans/dogecoin,nsacoin/nsacoin,Exceltior/dogecoin,masterbraz/dg,jarymoth/dogecoin,langerhans/dogecoin,riecoin/riecoin,masterbraz/dg,masterbraz/dg,nsacoin/nsacoin,jarymoth/dogecoin,nigeriacoin/nigeriacoin,coinkeeper/2015-06-22_18-37_dogecoin,riecoin/riecoin,coinkeeper/2015-06-22_18-37_dogecoin,Exceltior/dogecoin,oklink-dev/bitcoin_block,nigeriacoin/nigeriacoin,langerhans/dogecoin,coinwarp/dogecoin,marklai9999/Taiwancoin,riecoin/riecoin,langerhans/dogecoin,coinkeeper/2015-06-22_18-37_dogecoin,Exceltior/dogecoin,Exceltior/dogecoin,oklink-dev/bitcoin_block,oklink-dev/bitcoin_block,riecoin/riecoin,coinwarp/dogecoin,haisee/dogecoin,brishtiteveja/sherlockcoin,Exceltior/dogecoin,marklai9999/Taiwancoin,nigeriacoin/nigeriacoin,masterbraz/dg,brishtiteveja/sherlockcoin,RazorLove/cloaked-octo-spice,brishtiteveja/sherlockcoin,nigeriacoin/nigeriacoin,marklai9999/Taiwancoin,coinwarp/dogecoin,haisee/dogecoin,haisee/dogecoin,brishtiteveja/sherlockcoin,RazorLove/cloaked-octo-spice,riecoin/riecoin