New 'enumerated finite set library' by Lockwood Morris.  (As delivered.)
Corrections to get enum_fset/enumeralTheory to build.
Remove unnecessary dependency of enumfset/enumeralTheory on int.

This dependency is still present via totoTheory, because that theory
defines an order for the integers. But I think I might move that
definition out into a separate theory so that the core material
doesn't need to inherit the integers.