Rename HasDecorations api to SetDecorations api.

native/Avalonia.Native/inc/avalonia-native.h

@@ -247,7 +247,7 @@ AVNCOM(IAvnWindow, 04) : virtual IAvnWindowBase
 {
     virtual HRESULT ShowDialog (IAvnWindow* parent) = 0;
     virtual HRESULT SetCanResize(bool value) = 0;
-    virtual HRESULT SetHasDecorations(SystemDecorations value) = 0;
+    virtual HRESULT SetDecorations(SystemDecorations value) = 0;
     virtual HRESULT SetTitle (void* utf8Title) = 0;
     virtual HRESULT SetTitleBarColor (AvnColor color) = 0;
     virtual HRESULT SetWindowState(AvnWindowState state) = 0;

native/Avalonia.Native/src/OSX/window.mm

@@ -526,7 +526,7 @@ private:
         }
     }
     
-    virtual HRESULT SetHasDecorations(SystemDecorations value) override
+    virtual HRESULT SetDecorations(SystemDecorations value) override
     {
         @autoreleasepool
         {

src/Avalonia.Native/WindowImpl.cs

@@ -67,7 +67,7 @@ namespace Avalonia.Native
 
         public void SetSystemDecorations(Controls.SystemDecorations enabled)
         {
-            _native.HasDecorations = (Interop.SystemDecorations)enabled;
+            _native.Decorations = (Interop.SystemDecorations)enabled;
         }
 
         public void SetTitleBarColor (Avalonia.Media.Color color)