When applied to a term u and a theorem A |- !x::P. t, RESQ_SPEC
returns the theorem A, u IN P |- t[u/x]. If necessary, variables
will be renamed prior to the specialization to ensure that u is free
for x in t, that is, no variables free in u become bound after
substitution.
A |- !x::P. t
--------------------- RESQ_SPEC "u"
A, u IN P |- t[u/x]
Additionally, if the input theorem is a standard universal
quantification, then RESQ_SPEC behaves like SPEC.