Universally quantifies both sides of an equational theorem.
DESCRIBE
When applied to a variable x and a theorem A |- t1 = t2, whose conclusion
is an equation between boolean terms, FORALL_EQ returns the
theorem A |- (!x. t1) = (!x. t2), unless the variable x is free in any
of the assumptions.
A |- t1 = t2
------------------------ FORALL_EQ "x" [where x is not free in A]
A |- (!x.t1) = (!x.t2)
FAILURE
Fails if the theorem is not an equation between boolean terms, or if the
supplied term is not simply a variable, or if the variable is free in any of
the assumptions.