I need to add s3tc support to my Ubuntu 12.04 64bit installation. I have downloaded the mesa source (9.01) and on this page, http://dri.freedesktop.org/wiki/S3TC, it says something aboud libdxtn and enabling USE_EXTERNAL_DXTN_LIB=1 in the build (and I don't know what that means). Can anyone help me figure out how to do this?