UNPBETA_CONVPairRules.UNPBETA_CONV : (term -> conv)
Creates an application of a paired abstraction from a term.
The user nominates some pair structure of variables p
and a term t, and UNPBETA_CONV turns
t into an abstraction on p applied to
p.
------------------ UNPBETA_CONV "p" "t"
|- t = (\p. t) p
Fails if p is not a paired structure of variables.