#1039 distort map problems

[lucid]

if a distort map is on, the sprite is only drawn if x is between the left and right limits of the screen
this works at 0 z elevation, but if it is further, it gets cut off on the left and right sides of the screen

similarly, even at 0 z elevation, if a distort map distorts a sprite so it should be on screen, but the sprite would not be on screen if it were not distorted, it is not displayed

also, alpha values for pixels are ignored if a distort map is on,

in the following cap,
the trees are set to have a 1,1 distort map
mouse moves the dragon, w and s move in and out of the background
the green ground is on a separate layer, so it doesn't happen
but if you move the dragon behind a tree, you'll notice that the semi alpha edges of the trees are not displayed correctly
this happens whether only the foreground or background object has a distort map, (the dragon or the tree)
also, you can see the trees disappearing as they get close to the edge of the screen
there is a draw distance problem as well, when the camera zooms in and out
this is in addition to the other drawn distance zooming problem already reported ( http://sourceforge.net/tracker/?func=detail&aid=2830630&group_id=207820&atid=1003219 )
if I remove the distort maps from the trees, the zoom is set to limit itself so they don't disappear

http://dl.getdropbox.com/u/1013446/snakeglitches.exe