fix comment: B2DVector::angle ranges from -pi to +pi

Change-Id: I53f9bad932c0d389081575a0c99f1d86a872ea54
Reviewed-on: https://gerrit.libreoffice.org/38334Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

include/basegfx/vector/b2dvector.hxx

@@ -153,7 +153,7 @@ namespace basegfx
             The second 2D Vector
 
             @return
-            The Angle value of the two involved 2D Vectors in -pi/2 < return < pi/2
+            The Angle value of the two involved 2D Vectors ranging from -pi to +pi
         */
         double angle( const B2DVector& rVec ) const;