Skew bug with egl

[Bill Spitzak]

Further information:

Experimenting with resizing clickdot, it looks like it always skews such 
that line N is shifted width%16 pixels to the right of line N-1, where 0 
is the top of the window. I also see a width%16 line of garbage between 
the skewed left/right edges of the surface.

This implies that the *writing* code thinks the stride is a multiple of 
16, but the *reading* code thinks the stride is arbitrary. This is 
opposite of what I expected, but it seems the bug is in a disagreement 
between the compositor and clients over what stride to use. The clients 
seem to be using a stride that is a multiple of 16, but the compositor 
is using stride equal to the surface size.

The windows themselves are rectangular, so it looks like the bug is 
before the compositor combines them together. The resulting composite is 
drawn correctly to the window (though the x11-compositor width is 1024 
which may hide the problem here?).