bitmapButton now displays the image properly; solved assert failure in bitmapToggleButton
bitmapButton now displays the image properly; solved assert failure in bitmapToggleButton

See bug ticket 74 for the bitmapButton problem.
bitmapToggleButton triggered an assert failure, nullBitmap cannot be used,
therefore bitmapToggleButton now creates a bitmap with a single pixel.

Proclivis/wxHaskell,ekmett/wxHaskell,ekmett/wxHaskell,sherwoodwang/wxHaskell,sherwoodwang/wxHaskell,Proclivis/wxHaskell,Proclivis/wxHaskell,sherwoodwang/wxHaskell,ekmett/wxHaskell,sherwoodwang/wxHaskell,Proclivis/wxHaskell