announce: metabang-bind 0.7.4

I discovered a nasty bug in metabang-bind today caused by a gensym being created too early (i.e., it was created when I defined a macro rather than when a bind form in user-code was expanded.) Version 0.7.4 corrects this and adds a nifty new binding form: :structure/rw. This latter lets you both read and write to structure slots within the scope of a binding. Handy!