Tweak declarations of arguments for plP_fci2hex and plP_hex2fci.
Tweak declarations of arguments for plP_fci2hex and plP_hex2fci.

svn path=/trunk/; revision=5895

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