Implemented getGL() method in PLWJGL, but LWJGL not tested after latest

changes (removal of most static fields in PGraphicsOpenGL, PGL)

java/libraries/lwjgl/src/processing/lwjgl/PLWJGL.java

@@ -1996,4 +1996,9 @@ public class PLWJGL extends PGL {
   public void drawBuffer(int buf) {
     GL11.glDrawBuffer(buf);
   }
+
+
+  @Override
+  protected void getGL(PGL pgl) {
+  }
 }