Reworked the bridge detector to allow searching a single bridging

direction over multiple regions. This allows a single bridge to be
drawn over holes, which are too close to each other to allow
for separate bridges.
Fixes Bridging-Angle not optimal
https://github.com/prusa3d/Slic3r/issues/12

Re-allowed adaptive infill line width for solid infills. The adaptive
infill line width works in some circumstances, see Issue #15,
but the original implementation often changed the line width too
aggressively. The current implementation limits the line width change
to 20%.
Fixes Gaps between infill and perimeter leads to errors in laydown on following layer
https://github.com/prusa3d/Slic3r/issues/15

xs/xsp/BridgeDetector.xsp

@@ -29,5 +29,15 @@ BridgeDetector::new(expolygon, lower_slices, extrusion_width)
     OUTPUT:
         RETVAL
 
+BridgeDetector*
+BridgeDetector::new_expolygons(expolygons, lower_slices, extrusion_width)
+    ExPolygonCollection*    expolygons;
+    ExPolygonCollection*    lower_slices;
+    long                    extrusion_width;
+    CODE:
+        RETVAL = new BridgeDetector(expolygons->expolygons, *lower_slices, extrusion_width);
+    OUTPUT:
+        RETVAL
+
 %}
 };