Add more default net types

Previously Icarus only supported a default net type of wire or none.
This patch adds the rest of the supported net types (all except
uwire and trireg) to the `default_nettype directive. It also fixes
make_implicit_net_() to use the default_nettype instead of always
using implicit (the same as wire).

elab_net.cc

@@ -179,7 +179,7 @@ NetNet* PEIdent::make_implicit_net_(Design*des, NetScope*scope) const
       assert(nettype != NetNet::NONE);
 
       NetNet*sig = new NetNet(scope, peek_tail_name(path_),
-			      NetNet::IMPLICIT, 1);
+			      nettype, 1);
       sig->set_line(*this);
 	/* Implicit nets are always scalar logic. */
       sig->data_type(IVL_VT_LOGIC);

lexor.lex

@@ -485,13 +485,34 @@ S [afpnumkKMGT]
       if (strcmp(yytext,"wire") == 0) {
 	    net_type = NetNet::WIRE;
 
+      } else if (strcmp(yytext,"tri") == 0) {
+	    net_type = NetNet::TRI;
+
+      } else if (strcmp(yytext,"tri0") == 0) {
+	    net_type = NetNet::TRI0;
+
+      } else if (strcmp(yytext,"tri1") == 0) {
+	    net_type = NetNet::TRI1;
+
+      } else if (strcmp(yytext,"wand") == 0) {
+	    net_type = NetNet::WAND;
+
+      } else if (strcmp(yytext,"triand") == 0) {
+	    net_type = NetNet::TRIAND;
+
+      } else if (strcmp(yytext,"wor") == 0) {
+	    net_type = NetNet::WOR;
+
+      } else if (strcmp(yytext,"trior") == 0) {
+	    net_type = NetNet::TRIOR;
+
       } else if (strcmp(yytext,"none") == 0) {
 	    net_type = NetNet::NONE;
 
       } else {
 	    cerr << yylloc.text << ":" << yylloc.first_line
 		 << ": error: Net type " << yytext
-		 << " is not a valid (and supported)"
+		 << " is not a valid (or supported)"
 		 << " default net type." << endl;
 	    net_type = NetNet::WIRE;
 	    error_count += 1;