Backquote broken on SBCL again for defmacro/g!

Created by: equwal

defmacro/g! and friends don't work on SBCL 1.4.1 as far as I can tell. I've implemented the functionality using a reader macro, and can probably do it for defmacro! also. Maybe that would be a better route than having to track SBCL's development. Let me know what you think about this.