Build system bugfix.  Install C example source files regardless of ENABLE_gnome2.
Build system bugfix.  Install C example source files regardless of
ENABLE_gnome2.

svn path=/trunk/; revision=9214

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