Also trying to set displayWidth and displayHeight in init().

This fixes an issue where **displayWidth** and **displayHeight** are still 0 when used in sketchWidth() and sketchHeight(). This approach is described in the Processing [Wiki](http://wiki.processing.org/w/Window_Size_and_Full_Screen) to make a full-screen sketch that fills the whole screen without any borders.

See #2039 for more information.

### Code to reproduce the described bug

Run with *Present*.

```java
void draw() {
  background(52);

  stroke(255, 69, 0);

  line(0, 0, width, height);
  line(width, 0, 0, height);
}

public int sketchWidth() {
  return displayWidth;
}

public int sketchHeight() {
  return displayHeight;
}
```