BAT/KLFitter Incremental Build Fix, 1.0 branch (2018.09.21.)
I only noticed in https://gitlab.cern.ch/atlas/athena/merge_requests/14380 that BAT was not correctly re-built against the updated version of ROOT. This update "activates" the forcedownload step in BAT's build, forcing a re-download/re-build of it.
At the same time I also added a forcedownload step to KLFitter, as I'm not entirely sure whether that was correctly re-built or not. And now I realised that I should also add a forceconfigure step to KLFitter, just for added security. (Will do in an additional commit.)