Another complete revision of the formulae, and back
to analytic check of formula.  It is not going well!
slope() is my own numeric derivative.  This test shows it gives
same result as standard one; in particular the latter does not use a delta of 1.
Fix numeric log likelihood.  Yay!   analytic derivatives now check out.
Comment out, but retain, numerical test code.
This puts the system back into production mode.
Unfortunately, the MCTRACE remains completely flat.
Attempt to make the calculations more numerically stable.
Add MCTRACE2 to observe the iterations more closely.
Verified that numeric and analytic derivatives matched,
and solved the problem of NA's getting in both the derivatives
and input (q) values.
But the results are even wilder than before (q values often > 1e20, and the
resulting "chain" remains a constant.
useless tweak