Merge r5733:5850 from /nmap-exp/david/nmap-massping-migration.

Remove special-purpose log functions for graphing congestion control and other t
hings. There's enough information provided by -d3.

Update the congestion control graph program and add a program for graphing probe
s and drops.

Increase the initial ccthresh from 50 to 75.

Change how much the congestion threshold drops on packet drops.

Print group timing stats with -d2 and individual host timing stats with -d3.

Bump up the cc-graph.sh y axis limit to 80.

Put graphs in the same directory as their log file.

Go ahead and adjust timing for ICMP destination unreachables. I'm going to commi
t and experimental change to the congestion control that doesn't rely on this an
y more.

Scale group congestion control increments by the inverse of the packet
receipt ratio. This gives great performance without ignoring ICMP
destintation unreachable drops. This may be the breakthrough we've been
looking for.
I'll probably send a message about this later today. For information and        
graphs right now, see
http://www.bamsoftware.com/wiki/Nmap/ResponseRateScaledCongestionControl.
Sorry it's only in my nmap-massping-migration branch for now, but please
give it a try.

Only -d2 is now needed for cc-graph.sh.

Put a cap of 50 on the cwnd scaling factor.

Fix up the order of things in the packet_ratio debugging output.

Move the packet_ratio debugging output to printAnyStats and rearrange the order 
in which things are printed.

Put a header with the scan args at the top of the probes-graph.sh data files.

Add a function pcap_print_stats that shows the number of received and dropped pa
ckets for a descriptor.

Call pcap_print_stats after a run of ultra_scan.

Increase the congestion window less aggressively than before with -T4 and -T5 (s
till more aggressivly than with lesser timing values).

tcpip.cc

@@ -2091,6 +2091,20 @@ bool pcap_recv_timeval_valid() {
 #endif
 }
 
+/* Prints stats from a pcap descriptor (number of received and dropped
+   packets). */
+void pcap_print_stats(int logt, pcap_t *pd) {
+  struct pcap_stat stat;
+
+  assert(pd != NULL);
+
+  if (pcap_stats(pd, &stat) < 0) {
+    error("%s: %s\n", __func__, pcap_geterr(pd));
+    return;
+  }
+
+  log_write(logt, "pcap stats: %u packets received by filter, %u dropped by kernel.\n", stat.ps_recv, stat.ps_drop);
+}
 
 /* A trivial functon that maintains a cache of IP to MAC Address
    entries.  If the command is ARPCACHE_GET, this func looks for the