Sort out some minor memory management problems found by valgrind.
Sort out some minor memory management problems found by valgrind.

plotsh3d: initialize nsub to zero. valgrind detected that this uninitialized
value propagated to pldtik and was used there, but there were no practical
consequences because the returned value was ignored in whatever case.

plnxtvhi_draw:  replace

ptold = ((oldhiview[2 * i] < u[j] && i < mhi) || j >= n);

by

ptold = (j >= n || (i < mhi && oldhiview[2 * i] < u[j]));

the result is the same, but the rearranged order insures no read access
outside of oldhiview and u (which was being detected by valgrind).

svn path=/trunk/; revision=3784

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