Improve math module (#396)

* Improve math module

- Mark almost everything constexpr
- Equality (a == b) is now exact, down to the bit level. If you want approximate equality use the new ApproxEqual method/static method
- Rename Nz::Extend to Nz::Extent
- Removed Make[] and Set[] methods in favor of their static counterpart and operator=

src/Nazara/Widgets/AbstractTextAreaWidget.cpp

@@ -56,8 +56,8 @@ namespace Nz
 		textDrawer.Clear();
 		UpdateTextSprite();
 
-		m_cursorPositionBegin.MakeZero();
-		m_cursorPositionEnd.MakeZero();
+		m_cursorPositionBegin = Vector2ui::Zero();
+		m_cursorPositionEnd = Vector2ui::Zero();
 
 		RefreshCursor();
 	}