Merge in selected changes from profile.py on the trunk.  Note that
this is *not* a simple-minded merge from the code on the trunk -- that
does too much other stuff to be 100% safe for the 2.1.2 release
(e.g. getting rid of HotProfile and OldProfile, changing some methods
into global functions, a new calibration API).

Add the test_profile.py module which verifies that the profiler works
as expected.