RENDER_WITH and RENDER_HEIGHT

[Patrick Julien]

Boudewijn,

The reason why the pixmap is twice the value of RENDER_WIDTH and RENDER_HEIGHT 
is to try to draw tiles 4x4.

I.e. if you look at the big endian code, doing m_pixmap = img results in a new 
pixamp everytime.

doing m_pixmap.convertFromImage(img); will use the existing pixmap.  However, 
here, the problem is that you also need to check so that it falls on a 4x4 
tile boundary.