Rework handling of lexical scope

Move the storage of wires (signals) out of the Module class into
the PScope base class, and instead of putting the PWires all into
the Module object, distribute them into the various lexical scopes
(derived from PScope) so that the wire names do not need to carry
scope information.

This required some rewiring of elaboration of signals, and rewriting
of lexical scope handling.

Module.cc

@@ -54,16 +54,6 @@ void Module::add_function(perm_string name, PFunction *func)
       funcs_[name] = func;
 }
 
-PWire* Module::add_wire(PWire*wire)
-{
-      PWire*&ep = wires_[wire->path()];
-      if (ep) return ep;
-
-      assert(ep == 0);
-      ep = wire;
-      return wire;
-}
-
 void Module::add_behavior(PProcess*b)
 {
       behaviors_.push_back(b);
@@ -111,15 +101,6 @@ unsigned Module::find_port(const char*name) const
 }
 
 
-PWire* Module::get_wire(const pform_name_t&name) const
-{
-      map<pform_name_t,PWire*>::const_iterator obj = wires_.find(name);
-      if (obj == wires_.end())
-	    return 0;
-      else
-	    return (*obj).second;
-}
-
 PGate* Module::get_gate(perm_string name)
 {
       for (list<PGate*>::iterator cur = gates_.begin()