Prepare release notes for the current (5.10.0) stable release cycle.
Prepare release notes for the current (5.10.0) stable release cycle.

svn path=/trunk/; revision=12912

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