Add API to create wxGraphicsContext from win32 HDC

Add wxGraphicsContext::CreateFromNativeHDC() and wxGraphicsRenderer::
CreateContextFromNativeHDC() to allow creation not only from native
renderer object, but also from HDC, which is something universally
supported by win32 implementations.

interface/wx/graphics.h

@@ -482,6 +482,15 @@ public:
     */
     static wxGraphicsContext* CreateFromNativeWindow(void* window);
 
+    /**
+        Creates a wxGraphicsContext from a native DC handle. Windows only.
+
+        @see wxGraphicsRenderer::CreateContextFromNativeHDC()
+
+        @since 3.1.1
+    */
+    static wxGraphicsContext* CreateFromNativeHDC(WXHDC dc);
+
     /**
        Create a lightweight context that can be used only for measuring text.
     */
@@ -1321,6 +1330,13 @@ public:
     */
     virtual wxGraphicsContext* CreateContextFromNativeWindow(void* window) = 0;
 
+    /**
+        Creates a wxGraphicsContext from a native DC handle. Windows only.
+
+        @since 3.1.1
+    */
+    static wxGraphicsContext* CreateContextFromNativeHDC(WXHDC dc);
+
     /**
         Creates a wxGraphicsContext that can be used for measuring texts only.
         No drawing commands are allowed.