minor clean-up to Rect and Point.

- return "const" objects for overloaded operators to disallow constructs like: (a+b) = c;
- don't return references to non-static members, it's not always safe.
- Point.cpp was empty, so get rid of it
diff --git a/include/ui/Point.h b/include/ui/Point.h
index dbbad1e..1653120 100644
--- a/include/ui/Point.h
+++ b/include/ui/Point.h
@@ -31,12 +31,9 @@
     // because we want the compiler generated versions
 
     // Default constructor doesn't initialize the Point
-    inline Point()
-    {
+    inline Point() {
     }
-
-    inline Point(int _x, int _y) : x(_x), y(_y)
-    {
+    inline Point(int x, int y) : x(x), y(y) {
     }
 
     inline bool operator == (const Point& rhs) const {
@@ -57,8 +54,8 @@
     }
 
     inline Point& operator - () {
-        x=-x;
-        y=-y;
+        x = -x;
+        y = -y;
         return *this;
     }
     
@@ -73,11 +70,13 @@
         return *this;
     }
     
-    Point operator + (const Point& rhs) const {
-        return Point(x+rhs.x, y+rhs.y);
+    const Point operator + (const Point& rhs) const {
+        const Point result(x+rhs.x, y+rhs.y);
+        return result;
     }
-    Point operator - (const Point& rhs) const {
-        return Point(x-rhs.x, y-rhs.y);
+    const Point operator - (const Point& rhs) const {
+        const Point result(x-rhs.x, y-rhs.y);
+        return result;
     }    
 };