Rename benchmarks->millibenchmarks

Not quite as small as microbenchmarks, which primarily
test just a single feature, but not full benchmarks either.

millibenchmarks/allgroup.py

+# From https://mail.python.org/pipermail/pypy-dev/2014-May/012515.html
+
+
+def allgroup(expansions, n=0, groups = []):
+     expgroup = [expansions[n]]
+     if n == len(expansions) - 1:
+         yield groups + [expgroup]
+         for i in xrange(len(groups)):
+             tmp = groups[i]
+             groups[i] = tmp + expgroup
+             yield groups
+             groups[i] = tmp
+     else:
+         for g in allgroup(expansions, n+1, groups + [expgroup]):
+             yield g
+         for i in xrange(len(groups)):
+             tmp = groups[i]
+             groups[i] = tmp + expgroup
+             for g in allgroup(expansions, n + 1, groups):
+                 yield g
+             groups[i] = tmp
+
+count = 0
+for i in allgroup(range(11)):
+     count += 1
+print count