docs/using/install-client: client may work in other platforms
docs/using/install-client: client may work in other platforms

We know that it won't work on Windows as-is, but it probably does on
FreeBSD, NetBSD and OpenBSD.

jblancett/tsuru,gciotta/tsuru,RichardKnop/tsuru,cezarsa/tsuru,mderaldo/tsuru,guilhermebr/tsuru,cezarsa/tsuru,guilhermebr/tsuru,tuxmonteiro/tsuru,hugoantunes/tsuru,hcxiong/tsuru,kgrvamsi/tsuru,4eek/tsuru,guilhermebr/tsuru,tsuru/tsuru,4eek/tsuru,tuxmonteiro/tsuru,tsuru/tsuru,ggarnier/tsuru,mderaldo/tsuru,hcxiong/tsuru,gwmoura/tsuru,firebitsbr/tsuru,ArxdSilva/tsuru,ArxdSilva/tsuru,ggarnier/tsuru,RichardKnop/tsuru,ggarnier/tsuru,cgvarela/tsuru,gciotta/tsuru,ggarnier/tsuru,Endika/tsuru,ArxdSilva/tsuru,jblancett/tsuru,Endika/tsuru,mderaldo/tsuru,tuxmonteiro/tsuru,guilhermebr/tsuru,kgrvamsi/tsuru,Endika/tsuru,gwmoura/tsuru,cgvarela/tsuru,ArxdSilva/tsuru,tsuru/tsuru,hugoantunes/tsuru,tsuru/tsuru,cezarsa/tsuru,hcxiong/tsuru,gciotta/tsuru,firebitsbr/tsuru,4eek/tsuru,kgrvamsi/tsuru,gwmoura/tsuru,firebitsbr/tsuru,cezarsa/tsuru,jblancett/tsuru,cgvarela/tsuru,RichardKnop/tsuru