Fix warnings

Source/Charts/Utils/ChartUtils.swift

@@ -119,7 +119,7 @@ extension CGPoint
 extension CGContext
 {
 
-    open func drawImage(_ image: NSUIImage, atCenter center: CGPoint, size: CGSize)
+    public func drawImage(_ image: NSUIImage, atCenter center: CGPoint, size: CGSize)
     {
         var drawOffset = CGPoint()
         drawOffset.x = center.x - (size.width / 2)
@@ -157,7 +157,7 @@ extension CGContext
         NSUIGraphicsPopContext()
     }
 
-    open func drawText(_ text: String, at point: CGPoint, align: TextAlignment, anchor: CGPoint = CGPoint(x: 0.5, y: 0.5), angleRadians: CGFloat = 0.0, attributes: [NSAttributedString.Key : Any]?)
+    public func drawText(_ text: String, at point: CGPoint, align: TextAlignment, anchor: CGPoint = CGPoint(x: 0.5, y: 0.5), angleRadians: CGFloat = 0.0, attributes: [NSAttributedString.Key : Any]?)
     {
         let drawPoint = getDrawPoint(text: text, point: point, align: align, attributes: attributes)
         
@@ -175,7 +175,7 @@ extension CGContext
         }
     }
     
-    open func drawText(_ text: String, at point: CGPoint, anchor: CGPoint = CGPoint(x: 0.5, y: 0.5), angleRadians: CGFloat, attributes: [NSAttributedString.Key : Any]?)
+    public func drawText(_ text: String, at point: CGPoint, anchor: CGPoint = CGPoint(x: 0.5, y: 0.5), angleRadians: CGFloat, attributes: [NSAttributedString.Key : Any]?)
     {
         var drawOffset = CGPoint()