Moves a universal quantification outwards through a disjunction.
DESCRIPTION
When applied to a term of the form (!x.P) \/ (!x.Q), where x is free
in neither P nor Q, OR_FORALL_CONV returns the theorem:
|- (!x. P) \/ (!x. Q) = (!x. P \/ Q)
FAILURE
OR_FORALL_CONV fails if it is applied to a term not of the form
(!x.P) \/ (!x.Q), or if it is applied to a term (!x.P) \/ (!x.Q)
in which the variable x is free in either P or Q.