Merge Jay Fink's patch that puts UDP payloads in an external data file

instead of being hard-coded in payloads.cc. This is the patch from
http://seclists.org/nmap-dev/2010/q2/497.

payload.h

@@ -92,7 +92,10 @@
 #ifndef PAYLOAD_H
 #define PAYLOAD_H
 
+#define PAYLOAD_FILENAME "nmap-payloads"
+
 const char *get_udp_payload(u16 dport, size_t *length);
 const char *udp_port2payload(u16 dport, size_t *length);
+int init_payloads(void);
 
 #endif /* PAYLOAD_H */