Set limits to the "extrusion_multiplier" value and show warning message, if out of range value was inputted

src/libslic3r/PrintConfig.cpp

@@ -607,6 +607,7 @@ void PrintConfigDef::init_fff_params()
                    "this setting to get nice surface finish and correct single wall widths. "
                    "Usual values are between 0.9 and 1.1. If you think you need to change this more, "
                    "check filament diameter and your firmware E steps.");
+    def->max = 2;
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloats { 1. });
 
@@ -619,6 +620,7 @@ void PrintConfigDef::init_fff_params()
                    "If expressed as percentage (for example: 230%), it will be computed over layer height.");
     def->sidetext = L("mm or %");
     def->min = 0;
+    def->max = 1000;
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloatOrPercent(0, false));