Added a --proxies <chain> option to nmap to let users specify proxies to use

from command line.

<chain> is expected (by nsock) to be a comma-separated list of proxies.
e.g.:
  http://relay1.local:8080,http://relay2.local:3128

This option has currently no effect.

NmapOps.h

@@ -340,6 +340,8 @@ class NmapOps {
   FILE *inputfd;
   char *portlist; /* Ports list specified by user */
 
+  char *proxy_chain;
+
 #ifndef NOLUA
   int script;
   char *scriptargs;