- checkConv(.) now works with one *nested* list;   one argument 'ctrl' (no
  default!) instead of two ('control', 'checkCtrl')
- .makeCC() utility for constructing these"
- new: non-exported chk.cconv() and chk.convOpt() utilities
testthat -- new version:  expect_warning(<expr>, ....)
   now fails when there is an error after the warning
For now, just out-comment, using   " if(FALSE) .. Hadley .. "