Add gflops_ in curve filename

doc/doxygen/chapters/380_offline_performance_tools.doxy

@@ -515,12 +515,12 @@ The <c>-f</c> option can also be used to display the performance in terms of GFl
 
 \verbatim
 $ tools/starpu_perfmodel_plot -f -e -s non_linear_memset_regression_based_energy
-$ gnuplot starpu_non_linear_memset_regression_based_energy.gp
-$ gv starpu_non_linear_memset_regression_based_energy.eps
+$ gnuplot starpu_gflops_non_linear_memset_regression_based_energy.gp
+$ gv starpu_gflops_non_linear_memset_regression_based_energy.eps
 \endverbatim
 
-\image html starpu_non_linear_memset_regression_based_energy_flops.png
-\image latex starpu_non_linear_memset_regression_based_energy_flops.eps "" width=\textwidth
+\image html starpu_gflops_non_linear_memset_regression_based_energy.png
+\image latex starpu_gflops_non_linear_memset_regression_based_energy.eps "" width=\textwidth
 
 We clearly see here that it is much more energy-efficient to stay in the L3 cache.
 

tools/starpu_perfmodel_plot.c

@@ -507,7 +507,7 @@ static void display_selected_models(FILE *gnuplot_file, struct starpu_perfmodel
 	fprintf(gnuplot_file, "#!/usr/bin/gnuplot -persist\n");
 	fprintf(gnuplot_file, "\n");
 	fprintf(gnuplot_file, "set term postscript eps enhanced color\n");
-	fprintf(gnuplot_file, "set output \"starpu_%s%s.eps\"\n", options->energy_symbol?"power_":"", options->symbol);
+	fprintf(gnuplot_file, "set output \"starpu_%s%s.eps\"\n", options->energy_symbol?"power_":options->gflops?"gflops_":"", options->symbol);
 	fprintf(gnuplot_file, "set title \"Model for codelet %s\"\n", symbol);
 	fprintf(gnuplot_file, "set xlabel \"Total data size\"\n");
 	if (options->energy_symbol)