[API] Simplify flags API

imgui-binding/src/main/java/imgui/ImGuiViewport.java

@@ -51,6 +51,27 @@ public final class ImGuiViewport extends ImGuiStruct {
         IMGUI_VIEWPORT->Flags = flags;
     */
 
+    /**
+     * See {@link imgui.flag.ImGuiViewportFlags}.
+     */
+    public void addFlags(final int flags) {
+        setFlags(getFlags() | flags);
+    }
+
+    /**
+     * See {@link imgui.flag.ImGuiViewportFlags}.
+     */
+    public void removeFlags(final int flags) {
+        setFlags(getFlags() & ~(flags));
+    }
+
+    /**
+     * See {@link imgui.flag.ImGuiViewportFlags}.
+     */
+    public boolean hasFlags(final int flags) {
+        return (getFlags() & flags) != 0;
+    }
+
     /**
      * Main Area: Position of the viewport (the imgui coordinates are the same as OS desktop/native coordinates).
      */