Restore removed using statements from minimal classes.

src/OpenTK/Math/Point.cs

@@ -23,9 +23,11 @@
  // OTHER DEALINGS IN THE SOFTWARE.
  //
 
+#if MINIMAL
+using System;
+
 namespace OpenTK
 {
-#if MINIMAL
     /// <summary>
     /// Defines a point on a two-dimensional plane.
     /// </summary>
@@ -167,5 +169,5 @@ namespace OpenTK
             return X == other.X && Y == other.Y;
         }
     }
-#endif
 }
+#endif

src/OpenTK/Math/Rectangle.cs

@@ -23,9 +23,11 @@
  // OTHER DEALINGS IN THE SOFTWARE.
  //
 
+#if MINIMAL
+using System;
+
 namespace OpenTK
 {
-    #if MINIMAL
     /// <summary>
     /// Represents a rectangular region on a two-dimensional plane.
     /// </summary>
@@ -284,5 +286,5 @@ namespace OpenTK
                 Size.Equals(other.Size);
         }
     }
-#endif
 }
+#endif

src/OpenTK/Math/Size.cs

@@ -23,9 +23,11 @@
 // OTHER DEALINGS IN THE SOFTWARE.
 //
 
+#if MINIMAL
+using System;
+
 namespace OpenTK
 {
-#if MINIMAL
     /// <summary>
     /// Stores the width and height of a rectangle.
     /// </summary>
@@ -155,5 +157,5 @@ namespace OpenTK
         }
 
     }
-#endif
 }
+#endif

src/OpenTK/Minimal.cs

@@ -1,7 +1,5 @@
-#if !MINIMAL
-#endif
-
-#if ANDROID || IPHONE || MINIMAL
+#if ANDROID || IPHONE || MINIMAL
+using System;
 
 namespace OpenTK
 {