* (define-fun...) now has proper type checking in non-debug builds

* (define-fun...) now has proper type checking in non-debug builds
  (resolves bug #212)

* also closed some other type checking loopholes in SmtEngine

* small fixes to define-sort (resolves bug #214)

* infrastructural support for printing expressions in languages
  other than the internal representation language using an IO
  manipulator, e.g.:

    cout << Expr::setlanguage(language::output::LANG_SMTLIB_V2) << expr;

  main() sets the output language for all streams to correspond to
  the input language

* support delaying type checking in debug builds, so that one can debug
  the type checker itself (before it was difficult, because debug builds did
  all the type checking on Node creation!): new command-line flag
  --no-early-type-checking (only makes sense for debug builds)

* disallowed copy-construction of ExprManager and NodeManager, and made other
  constructors explicit; previously it was easy to unintentionally create
  duplicate managers, with really weird results (i.e., disappearing
  attributes!)