ns-3 print routing tables

This is a proposed merge patch for bugs 947 and 963.  It pretty prints Ipv4 routing tables at specified times.

Sample output (can be seen from running the modified examples):

AODV example (examples/routing/aodv.cc printRoutes=1):
Node: 0 Time: 8s
AODV Routing table
Destination     Gateway         Interface       Flag    Expire          Hops
10.0.0.2        10.0.0.2        10.0.0.1        UP      3.00            1
10.0.0.10       10.0.0.2        10.0.0.1        DOWN    11.02           9
10.255.255.255  10.255.255.255  10.0.0.1        UP      9223372028.85   1
127.0.0.1       127.0.0.1       127.0.0.1       UP      9223372028.85   1

OLSR example (examples/wifi/wifi-simple-adhoc-grid tracing=1):
Node: 24 Time: 30s Ipv4ListRouting table
  Priority: 10 Protocol: ns3::olsr::RoutingProtocol
Destination     NextHop         Interface       Distance
10.1.1.1        10.1.1.20       1               8       
10.1.1.2        10.1.1.20       1               7       
10.1.1.3        10.1.1.20       1               6       
10.1.1.4        10.1.1.20       1               5       

Nix example (examples/routing/nix-simple.cc)
Node: 0 Time: 8s Ipv4ListRouting table
  Priority: 10 Protocol: ns3::Ipv4NixVectorRouting
NixCache:
Destination     NixVector
10.1.3.2        011
Ipv4RouteCache:
Destination     Gateway         Source            OutputDevice
10.1.3.2        10.1.1.2        10.1.1.1          1

Global/static routing examples (examples/routing/dynamic-global-routing.cc)
 (formatted like "route -n", and note use of List routing table)
Node: 6 Time: 12s Ipv4ListRouting table
  Priority: 0 Protocol: ns3::Ipv4StaticRouting
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
127.0.0.0       0.0.0.0         255.0.0.0       U     -      -      -   0
10.1.3.0        0.0.0.0         255.255.255.0   U     -      -      -   1
172.16.1.0      0.0.0.0         255.255.255.0   U     -      -      -   2
  Priority: -10 Protocol: ns3::Ipv4GlobalRouting
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.1.3.1        0.0.0.0         UG    -      -      -   1

[Elena Buchatskaia, 2010-12-14 19:56:02]

http://codereview.appspot.com/3613041/diff/1/src/routing/aodv/aodv-rtable.cc
File src/routing/aodv/aodv-rtable.cc (left):

http://codereview.appspot.com/3613041/diff/1/src/routing/aodv/aodv-rtable.cc#...
src/routing/aodv/aodv-rtable.cc:402: Purge ();
Removing Purge() call may cause incorrect output, such as entries with negative
time value, wrong flags or simply entries, which must be removed. AODV manages
its routing table only when it is necessary, without any special timers. This
implementation, providing a correct behavior, reduces the number of function
calls. Is it essential to make Print function constant?

[Tom Henderson, 2010-12-15 05:35:47]

> Is it essential to make Print function constant?

Not essential, but I think it is preferable to make Print() a const function in
general, so I suggest in revision 2 a version of Purge() that works with a const
Print() (create a copy of the table, purge the copy, then print it).  What do
you think?

[Pavel Boyko, 2010-12-16 17:24:12]

Good feature, vote to merge it.

http://codereview.appspot.com/3613041/diff/3001/src/routing/aodv/aodv-rtable.cc
File src/routing/aodv/aodv-rtable.cc (right):

http://codereview.appspot.com/3613041/diff/3001/src/routing/aodv/aodv-rtable....
src/routing/aodv/aodv-rtable.cc:185: std::setw (14) << (m_lifeTime -
Simulator::Now ()).GetSeconds ();
Please treat m_lifeTime == Simulator::GetMaximumSimulationTime() separately,
e.g. print "Never" in the "Expire" column.

Overall, PrintRoutingTable() looks useful.