opengl: offscreen use GL_PACK_ALIGNMENTas

Thanks to https://stackoverflow.com/revisions/14324292/36

Author: cirosantilli

opengl/offscreen.c

@@ -301,7 +301,7 @@ static void init(void)  {
 
     glClearColor(0.0, 0.0, 0.0, 0.0);
     glEnable(GL_DEPTH_TEST);
-    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+    glPixelStorei(GL_PACK_ALIGNMENT, 1);
     glViewport(0, 0, width, height);
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();