Added plGetName for building up file name specs out of path components. Also moved some utility functions from plstream.c here.
Added plGetName for building up file name specs out of path components.
Also moved some utility functions from plstream.c here.

svn path=/trunk/; revision=461

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