It's top-bottom not bottom-top in GL space. (#1517)

src/rlgl.h

@@ -1100,7 +1100,7 @@ void rlFrustum(double left, double right, double bottom, double top, double znea
 // Multiply the current matrix by an orthographic matrix generated by parameters
 void rlOrtho(double left, double right, double bottom, double top, double znear, double zfar)
 {
-    if (((right - left) > 0) && ((bottom - top) > 0))
+    if (((right - left) > 0) && ((top - bottom) > 0))
     {
         Matrix matOrtho = MatrixOrtho(left, right, bottom, top, znear, zfar);
         *RLGL.State.currentMatrix = MatrixMultiply(*RLGL.State.currentMatrix, matOrtho);