Created attachment 115778 [details] [review]
Patch

I tried it and I really like it, unfortunately I cant commit it
because it has errors, you missed the warning icons that show up
for deprecated/unavailable properties.

For a quick look, just fire up glade w/ patch applied and create 
a window, set the target gtk+ version to 2.10 or 2.8 via Edit -> Preferences
and scroll through the props window, see clipped text.

Ok I liked it so much I went and rewrote it a little cleaner.

all the size-allocate/request signaling is now done straight
in glade-editor-property.c, the input portion now resized larger
and unfortunately I was unable to Right align all the labels,
so they are left aligned, but all resizing and word wrapping
is working beautifully, and now it takes the warning icon into
consideration.

closing this one, thanks for the inspiration ;-)