Trivial: print "No free event buffers" warning to stderr instead of stdout

[JohnPJenkins]

tw-sched.c, line 180

[laprej]

Is this different enough from 719d8e4 to make it worthwhile? Are you running into a situation where that logic is not being tripped but you're still reaching a problem state?

[JohnPJenkins]

I simply want the message that's currently printed to go to stderr rather than stdout (ie fprintf(stderr, ...) rather than printf(...)`). In many of my experiments I redirect stdout and stderr to different files to make it easier to grep through the resulting output.

Relatedly, I would love for there to be an option to kill the simulation after N consecutive failed "allocation" attempts. E.g., last evening before I left I set up a sweep of ~700 simulations, the 10th of which entered an infinite "buffers not available" loop I then killed this morning. A "g_tw_max_consec_nobuf_ct" or something (defaulting to ULONG_MAX or similar) would do the trick, along with a bit of extra logic to track and reset the failure count accordingly. Basically, an "opt-in" workaround for issue #6.