Corrected an issue that produces potentially incorrect output

from ext2spice due to "equiv" statements in the .ext file.  The
algorithm was not properly keeping the port as the preferred
name of the node, resulting in the non-preferred name being
used instead of the port name in the output.  This would happen
only if there was a label on a net that had a different name than
the port name.  The error became much more prevalent after changing
the extract behavior to make "extract do aliases" default.  Also
fixed a somewhat related minor error in which magic would print an
error message about ports being shorted together on the same kind
of net where both a port and a (different) label were attached to
the net.  Since the non-port label is not a preferred name, then
there should be no warning message.  The warning is only intended
for cases where two (or more) ports are truly shorted together.

extract/ExtBasic.c

@@ -793,7 +793,11 @@ extOutputNodes(nodeList, outFile)
 						    text, ll->ll_label->lab_text);
 				    lastname = ll->ll_label->lab_text;
 				}
+				/* Don't print a warning unless both labels are
+				 * really ports.
+				 */
 				if ((portname != NULL) &&
+			    		    (ll->ll_attr == LL_PORTATTR) &&
 					    (strcmp(ll->ll_label->lab_text, portname)))
 				    TxError("Warning:  Ports \"%s\" and \"%s\" are"
 					    " electrically shorted.\n",