gstreamer: fix types for event handlers in Element.chs
gstreamer: fix types for event handlers in Element.chs

darcs-hash:20070720201151-21862-bdb8a50b8a8467e1d15227d2745e6e69d95b7cf9.gz

thiagoarrais/gtk2hs,thiagoarrais/gtk2hs,thiagoarrais/gtk2hs