Added core.game.setRealtime(freq) function to set the engine into realtime...

Added core.game.setRealtime(freq) function to set the engine into realtime mode, calling tick() at the given frequency
Added an example_realtime module that is an exact copy of example module but in realtime (the gameplay sucks it's not adapted)


git-svn-id: http://svn.net-core.org/repos/t-engine4@1125 51575b47-30f0-44d4-a5cc-537603b46e54