Refine the filter_rpath function a little more by removing empty elements from the rpath list.
Refine the filter_rpath function a little more by removing empty
elements from the rpath list.

svn path=/trunk/; revision=12877

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