Reorganized width code a bit.  Also took out gdImageSetThickness call in plD_init_png.  It's arguments were not initialized properly (causing segfaults on Linux), but it was redundant in any case so it was just removed rather than fixed.
Reorganized width code a bit.  Also took out gdImageSetThickness call in
plD_init_png.  It's arguments were not initialized properly (causing
segfaults on Linux), but it was redundant in any case so it was just
removed rather than fixed.

svn path=/trunk/; revision=3341

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