print -> info; end the horror of print vs. print()

Although we could use print() from __future__, this messes
up scripts which use examples as modules.

The simple, if not nicest for 2.7, solution is to use
info(), output() and other mininet.log functions. The disadvantage
is that we may have to adjust things if we change info() to
add automatic newlines, but we can burn that bridge in Mininet
3.x.

examples/popen.py

@@ -9,7 +9,7 @@ pmonitor()
 from mininet.net import Mininet
 from mininet.node import CPULimitedHost
 from mininet.topo import SingleSwitchTopo
-from mininet.log import setLogLevel
+from mininet.log import setLogLevel, info
 from mininet.util import custom, pmonitor
 
 def monitorhosts( hosts=5, sched='cfs' ):
@@ -28,7 +28,7 @@ def monitorhosts( hosts=5, sched='cfs' ):
     # Monitor them and print output
     for host, line in pmonitor( popens ):
         if host:
-            print( "<%s>: %s" % ( host.name, line.strip() ) )
+            info( "<%s>: %s" % ( host.name, line ) )
     # Done
     net.stop()