major IOS regressing related to clipping

[ddyer0]

This has been in the last 2 weekly updates, I'm only just getting around to documenting it.
It appears that when using clipRect to combine a completely-outside rectangle, so nothing
should be visible, the clipping region is completely forgotten and the whole screen is writable.

Here's a test picture (as produced by simulator and android)

here's a very buggy test picture produced by IOS, the light green color fulling the whole
screen and the small black rectangle at the lower right are both incorrect, they should have
been clipped to nothing.

test program

Dtest.java