[plt-scheme] 3.99.0.7: `equal?' and structure types

[Matthew Flatt]

As of version 3.99.0.7 in SVN, `equal?' and hashing work on cyclic data.

Also, the new `prop:equal+hash' property lets you specify an equality
predicate and hash-code functions for a structure type. See the
documentation for details.

Inside MzScheme, scheme_set_type_equality() has changed to accommodate
cyclic data.

Matthew