Some CurveLocation cleanup.

- Remove UID as there is no need anymore
- Rename some private properties

src/path/CurveLocation.js

@@ -51,17 +51,13 @@ var CurveLocation = Base.extend(/** @lends CurveLocation# */{
                 curve = next;
             }
         }
-        // Define this CurveLocation's unique id.
-        // NOTE: We do not use the same pool as the rest of the library here,
-        // since this is only required to be unique at runtime among other
-        // CurveLocation objects.
-        this._id = UID.get(CurveLocation);
         this._setCurve(curve);
         this._time = time;
         this._point = point || curve.getPointAtTime(time);
         this._overlap = _overlap;
         this._distance = _distance;
-        this._intersection = this._next = this._prev = null;
+        // Properties related to linked intersection locations
+        this._intersection = this._next = this._previous = null;
     },
 
     _setCurve: function(curve) {

src/path/PathItem.Boolean.js

@@ -206,7 +206,7 @@ PathItem.inject(new function() {
         while (prev) {
             if (prev === to)
                 return;
-            prev = prev._prev;
+            prev = prev._previous;
         }
         // Now walk to the end of the existing chain to find an empty spot, but
         // stop if we find `to`, to avoid adding it again.
@@ -215,10 +215,10 @@ PathItem.inject(new function() {
         // If we're reached the end of the list, we can add it.
         if (!from._next) {
             // Go back to beginning of the other chain, and link the two up.
-            while (to._prev)
-                to = to._prev;
+            while (to._previous)
+                to = to._previous;
             from._next = to;
-            to._prev = from;
+            to._previous = from;
         }
     }