Broke pldtik() into two functions -- pldtik(), which handles only tick spacing, and pldprec(), which handles only precision and significant digits settings.  Each substantially clarified in the process.
Broke pldtik() into two functions -- pldtik(), which handles only tick
spacing, and pldprec(), which handles only precision and significant
digits settings.  Each substantially clarified in the process.

svn path=/trunk/; revision=1427

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