Do not require picins.sty.
https://bugs.gentoo.org/577828#c4

--- gnuplot/docs/Makefile.am
+++ gnuplot/docs/Makefile.am
@@ -179,9 +179,10 @@
 	$(AM_V_at)GNUPLOT_LIB=$(top_srcdir)/demo $(GNUPLOT_EXE) $(srcdir)/plotstyles.gnu
 	  rm -f gpinsetfigure.tex ; \
 	  ( echo "\usepackage{graphicx}" > gpinsetfigure.tex ; \
-	    echo "\usepackage{picins}" >> gpinsetfigure.tex ; \
 	    echo "\newcommand{\gpinsetfigure}[1]{" >> gpinsetfigure.tex ; \
-	    echo "  \parpic[r][rt]{\includegraphics[width=3in,keepaspectratio]{#1}}" >> gpinsetfigure.tex ; \
+	    echo "  \begin{figure}[htb]" >> gpinsetfigure.tex ; \
+	    echo "  \centering\includegraphics[width=3in,keepaspectratio]{#1}" >> gpinsetfigure.tex ; \
+	    echo "  \end{figure}" >> gpinsetfigure.tex ; \
 	    echo "}" >> gpinsetfigure.tex ; \
 	  ) ; \
 	$(AM_V_GEN)touch $@