infinite loop in spice parser

Hi Al, hi list.

playing with spicelib, i found the parser hanging at
gnucap-spice>C1 0 1 2;

while its not exceptionally clever to place that semicolon, it's still a
gnucap bug.

i fixed it with

     cmd >> node_name;
+    if(spots.back() == cmd.cursor()) {
+      throw Exception("what's this?");
+    }
     spots.push_back(cmd.cursor());

in count_ports. now i get
gnucap-spice>C1 0 1 2;
C1 0 1 2;
        ^ ? what's this?

regards
felix