Fix regression about percent extrusion width not being validated. Includes regression test

lib/Slic3r/Config.pm

@@ -325,7 +325,7 @@ sub validate {
         my $max_nozzle_diameter = max(@{ $self->nozzle_diameter });
         die "Invalid extrusion width (too large)\n"
             if defined first { $_ > 10 * $max_nozzle_diameter }
-                map $self->get_value("${_}_extrusion_width"),
+                map $self->get_abs_value_over("${_}_extrusion_width", $self->layer_height),
                 qw(perimeter infill solid_infill top_infill support_material first_layer);
     }
     
@@ -355,6 +355,8 @@ sub validate {
             }
         }
     }
+    
+    return 1;
 }
 
 sub replace_options {