This implements the menu shadow changes proposed in D9549; now we use a combobox with your options (None, Small, Normal, and Large) to choose the window shadow size. Normal is what we recently changed the default to (and this remains the new default) and Small is the old default value for people who preferred that. Menu shadows are now 25% the size of the main window shadows for Normal and Large, 37% for Small, and 0% for None.
I had a massive amount of help from @hpereiradacosta; in fact, probably 75% of these changes are his. It's a shame multiple authorship ian's possible. Hugo, feel free to comandeer the revision if you'd like the credit!