Remove link to development list, make stable link point to 5.8.0-RC1.
Remove link to development list, make stable link point to 5.8.0-RC1.

svn path=/trunk/; revision=7962

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