You should not ever ever ever call cairo_reset_clip(). If you do, your
code is broken and you deserve everything you get.
And we should definitely not support this insanity.
We used to handle zero height/width specially in the non-double buffered
case due to the weird behaviour of XClearArea in this case. However
this is undocumented, incompatible with what happens on double-buffered
drawing, and just not a good API. So, we drop this behaviour, having
fixed gtkclist.c which used this.
