Replaced some deprecated functions on OS X

NSWindow convertBaseToScreen: -> convertRectToScreen:
NSView   convertPointToBase:  -> convertPointToBacking:

src/SFML/Window/OSX/SFOpenGLView.mm

@@ -174,16 +174,19 @@ BOOL isValidTextUnicode(NSEvent* event);
 }
 
 
+////////////////////////////////////////////////////////
+-(NSPoint)convertPointToScreen:(NSPoint)point
+{
+    NSRect rect = NSZeroRect;
+    rect.origin = point;
+    rect = [[self window] convertRectToScreen:rect];
+    return rect.origin;
+}
+
+
 ////////////////////////////////////////////////////////
 -(NSPoint)computeGlobalPositionOfRelativePoint:(NSPoint)point
 {
-    // Note : -[NSWindow convertBaseToScreen:] is deprecated on 10.7
-    //        but the recommended -[NSWindow convertRectToScreen] is not
-    //        available until 10.7.
-    //
-    //        So we stick with the old one for now.
-
-
     // Flip SFML coordinates to match window coordinates
     point.y = [self frame].size.height - point.y;
 
@@ -192,7 +195,7 @@ BOOL isValidTextUnicode(NSEvent* event);
     point = [self convertPoint:point toView:nil]; // nil means window
 
     // Convert it to screen coordinates
-    point = [[self window] convertBaseToScreen:point];
+    point = [self convertPointToScreen:point];
 
     // Flip screen coordinates to match CGDisplayMoveCursorToPoint referential.
     const float screenHeight = [[[self window] screen] frame].size.height;

src/SFML/Window/OSX/SFWindowController.mm

@@ -343,7 +343,7 @@
     const NSPoint origin = [m_oglView frame].origin;
     const NSSize  size = [m_oglView frame].size;
     const NSPoint topLeftCornerOfView = NSMakePoint(origin.x, origin.y + size.height);
-    const NSPoint positionInView = [m_oglView convertPointToBase:topLeftCornerOfView];
+    const NSPoint positionInView = [m_oglView convertPointToBacking:topLeftCornerOfView];
 
     // Then, convert it to window base system
     const NSPoint positionInWindow = [m_oglView convertPoint:positionInView toView:nil];