A whole bunch of cleanups to state.Lock.

Now t/curse passes again when parallelized (except for the countall
mismatch, since we haven't fixed the source of that problem yet).  At least
it's consistent now.

There's a bunch of stuff rearranged in here, but the actual important
problem was that we were doing unlink() on the lock fifo even if ENXIO,
which meant a reader could connect in between ENXIO and unlink(), and thus
never get notified of the disconnection.  This would cause the build to
randomly freeze.

helpers.py

@@ -36,6 +36,7 @@ def mkdirp(d, mode=None):
 def log_(s):
     sys.stdout.flush()
     sys.stderr.write(s)
+    #sys.stderr.write('%d %s' % (os.getpid(), s))
     sys.stderr.flush()