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.

PWire.h

@@ -56,13 +56,13 @@ enum PWSRType {SR_PORT, SR_NET, SR_BOTH};
 class PWire : public LineInfo {
 
     public:
-      PWire(const pform_name_t&hname,
+      PWire(perm_string name,
 	    NetNet::Type t,
 	    NetNet::PortType pt,
 	    ivl_variable_type_t dt);
 
 	// Return a hierarchical name.
-      const pform_name_t&path() const;
+      perm_string basename() const;
 
       NetNet::Type get_wire_type() const;
       bool set_wire_type(NetNet::Type);
@@ -90,7 +90,7 @@ class PWire : public LineInfo {
       NetNet* elaborate_sig(Design*, NetScope*scope) const;
 
     private:
-      pform_name_t hname_;
+      perm_string name_;
       NetNet::Type type_;
       NetNet::PortType port_type_;
       ivl_variable_type_t data_type_;