Specialize return types on copy.

src/main/java/pythagoras/d/AffineTransform.java

@@ -362,7 +362,7 @@ public class AffineTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public AffineTransform copy () {
         return new AffineTransform(m00, m01, m10, m11, tx, ty);
     }
 

src/main/java/pythagoras/d/IdentityTransform.java

@@ -109,7 +109,7 @@ public class IdentityTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public IdentityTransform copy () {
         return this;
     }
 

src/main/java/pythagoras/f/AffineTransform.java

@@ -362,7 +362,7 @@ public class AffineTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public AffineTransform copy () {
         return new AffineTransform(m00, m01, m10, m11, tx, ty);
     }
 

src/main/java/pythagoras/f/IdentityTransform.java

@@ -109,7 +109,7 @@ public class IdentityTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public IdentityTransform copy () {
         return this;
     }