22 April 2009.  The coxph code had an override to iter and eps, making both of
them more strict for a penalized model.  However, the overall default values
have changed over time, so that these lines actually decreased accuracy - the
opposite of their intent.  Removed the lines.  Also removed the iter.miss and
eps.miss components (on which this check depended) from coxph.control, which
makes that function match its documentation.

1 May 2009. The anova.coxph function was incorrect for models with a strata
term.  Fixed this, and made chisquare tests the default.

20 May 2009.  The manual page for survfit was confusing, since it tries to 
document both the standard KM (formula method) and the coxph method.  I've
split them out so that now survfit documents only the basic method and points 
a user the appropriate specialized page.

21 May 2009 Create a test case for factor variables/newdata/predict for coxph 
and survreg.  This led to a set of minor fixes; the code is now in line with
the R standard for model functions.  One consequence is that model.frame.coxph
and model.frame.survreg are no longer needed, so have been removed.

22 May 2009: Allow single subscripts to rate tables, e.g. survexp[1:10].  
Returns a simple vector of values.  The str() function does this to print out
a short summary.  Problem pointed out by Heinz Tuechler.

2 June 2009: Surv(time1, time2, status, type='interval') would fail for an NA
status code.  Pointed out by Achim Zeilus.

10 June 2009: Fix an error pointed out by Nick Reich, who was the first to use
interval censored data + user defined distribution in survreg, jointly.  There
was no test case and creating one uncovered several errors (but only for this
combination).  All the error cases led to catastrophic failure, highlighting
the extreme rarity of a user requesting this combination.

17 Aug 2009: Small bug in survfit.coxph.null pointed out by Frank Harrell.  The
'n' component would be missing if the input data included strata, i.e., the
initial model had used x=TRUE.  He also pointed out the fix.

20 Aug 2009: One more fix to predict.coxph.  It needed to use 
delete.response(Terms) rather than Terms, so as to not look for (unnecessarily) 
the response variable when the newdata argment is used.  Pointed out by Michael
Conklin.

4 Sep 2009: Added a model.matrix.coxph and model.frame.coxph methods.  The
model.matrix.default function ceased to work for coxph models sometime
between R 2.9 and 2.9.2 (best guess).  This wasn't picked up in the test
suite but rather by failure of 3 packages that depend on survival.  Also added
a test.  Update CRAN since this broke other's packages.