add comment about likely broken functionality for font validation - refs #1415
add comment about likely broken functionality for font validation - refs #1415

tizzybec/tilemill,nyimbi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,fxtentacle/tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,mbrukman/tilemill,nyimbi/tilemill,tilemill-project/tilemill,paulovieira/tilemill-clima,Teino1978-Corp/Teino1978-Corp-tilemill,fxtentacle/tilemill,florianf/tileoven,nyimbi/tilemill,tizzybec/tilemill,mbrukman/tilemill,florianf/tileoven,florianf/tileoven,tizzybec/tilemill,Zhao-Qi/tilemill,paulovieira/tilemill-clima,paulovieira/tilemill-clima,MappingKat/tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,fxtentacle/tilemill,nyimbi/tilemill,mbrukman/tilemill,mbrukman/tilemill,tizzybec/tilemill,nyimbi/tilemill,paulovieira/tilemill-clima,Teino1978-Corp/Teino1978-Corp-tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,MappingKat/tilemill,fxtentacle/tilemill,tilemill-project/tilemill,paulovieira/tilemill-clima,tilemill-project/tilemill,mbrukman/tilemill,fxtentacle/tilemill,Zhao-Qi/tilemill,tizzybec/tilemill