EXISTS_OR_CONVConv.EXISTS_OR_CONV : conv
Moves an existential quantification inwards through a disjunction.
When applied to a term of the form ?x. P \/ Q, the
conversion EXISTS_OR_CONV returns the theorem:
|- (?x. P \/ Q) = (?x.P) \/ (?x.Q)
Fails if applied to a term not of the form
?x. P \/ Q.
Conv.OR_EXISTS_CONV, Conv.LEFT_OR_EXISTS_CONV,
Conv.RIGHT_OR_EXISTS_CONV