+0.5.7 - .../01/2009 - Pàdoa release
+ * generation of derived lemmas rewritten to be based on hooks that
+ are triggered every definition
+ * composition of coercions fixed, more composite are generated
+ * undo mechanism for coercions remade, should work better
+ * new command "prefer coercion foo" to reorder coercions.
+ * UTF-8 eq classes and virtuals described in the manual and
+ consistently printed in the TeX/UTF-8 table
+ * added a memory system for UTF-8 equivalence classes, so that
+ last choice is remembered and attempted first next time the same
+ eq class is walked trough