Update to 2.8.12 version of ExternalProject.cmake with tar.xz patch applied.
Update to 2.8.12 version of ExternalProject.cmake with tar.xz patch
applied.

svn path=/trunk/; revision=12588

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot