Replace plshade/plcont use with plshades use. Also, restore default color at end.
Replace plshade/plcont use with plshades use.
Also, restore default color at end.

The results were identical to the equivalent python result, and this
constitutes a good first test of the plshades functionality (including
coordinate wrapping) just implemented in tclAPI.c.

This concludes the current round of implementing plshades and
getting the coordinate wrapping right for plcont, plshade, and plshades
in tclAPI.c and testing the results with x09.tcl, x15.tcl, x16.tcl (historical
plshade/plcont version) and x16.tcl (current plshades version).

svn path=/trunk/; revision=3667

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