Refactored Perimeter code with new Slic3r::Polygon and Slic3r::ExPolygon objects

Large refactoring. Speed gains. Removed convex hull for bridges.

lib/Slic3r/Polygon.pm

@@ -0,0 +1,30 @@
+package Slic3r::Polygon;
+use strict;
+use warnings;
+
+# a polygon is a closed polyline.
+# if you're asking why there's a Slic3r::Polygon as well
+# as a Slic3r::Polyline::Closed you're right. I plan to
+# ditch the latter and port everything to this class.
+
+use Slic3r::Geometry qw(polygon_remove_parallel_continuous_edges);
+
+# the constructor accepts an array(ref) of points
+sub new {
+    my $class = shift;
+    my $self;
+    if (@_ == 1) {
+        $self = [ @{$_[0]} ];
+    } else {
+        $self = [ @_ ];
+    }
+    bless $self, $class;
+    $self;
+}
+
+sub cleanup {
+    my $self = shift;
+    polygon_remove_parallel_continuous_edges($self);
+}
+
+1;