Merge pull request #954 from Rishab87/unexpected-y-axis

Fixed unexpected Y-axis translation when using ```ortho()``` and ```resetMatrix()```

Author: Stefterv

core/src/processing/opengl/PGraphicsOpenGL.java

@@ -4481,7 +4481,7 @@ public void ortho(float left, float right,
 
     // The minus sign is needed to invert the Y axis.
     projection.set(x,  0, 0, tx,
-                   0, -y, 0, ty,
+                   0, -y, 0, -ty,
                    0,  0, z, tz,
                    0,  0, 0,  1);