RESQ_REWRITE1_CONV is a rewriting conversion similar to
COND_REWRITE1_CONV. The only difference is the rewriting theorem it
takes. This should be an equation with restricted universal
quantification at the outer level. It is converted to a theorem in the
form accepted by the conditional rewriting conversion.
Suppose that th is the following theorem
evaluating RESQ_REWRITE1_CONV thms th "t[x']"
will return a theorem
   A, P x' |- t[x'] = t'[x']