Add -DPLD_extqt to the compile flags that are delivered by pkg-config.
Add -DPLD_extqt to the compile flags that are delivered by pkg-config.

svn path=/trunk/; revision=9815

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