For the full log of gretl changes since January 2000, see
<@url="http://gretl.sourceforge.net/ChangeLog.html">.

2018-12-21 version 2018d
- Internal representation of missing values: switch to
  using NaN
- Internal speed-ups for matrix reads and writes
- Add new function, atan2(), as per the C function of the
  same name
- Add new function isocountry(): maps between the various
  designations for countries (full name and codes) in the ISO
  3166 standard
- Add new function hyp2f1(): Gauss hypergeometric function
- cdemean() function: add option to standardize in addition
  to centering
- boxcox() function: accept a matrix argument
- psdroot() function: add option to check for positive
  semidefinite status of matrix argument
- cdf() function: add support for logistic (code "lgt")
- "install" command: replace with new "pkg" command (but the
  old form still works until further notice)
- "levinlin" command: add a --verbose option and fix some
  bugs
- "arima" command with --x-12-arima option: enable the $vcv
  accessor
- "dpanel" command: add --keep-extra option to enable access
  to the GMM weights and instrument matrices after estimation
- Native arima: improve the scaling of dependent series
  when necessary
- Line plots via gnuplot: show gaps for missing values
- dbnomics: some refinements to handle problematic cases
  as well as some new functionality
- Matrix power (A^k): support fractional and negative powers
  for positive-definite matrices
- Fix bug: out-of-bounds writes to matrices were not being
  caught under all conditions
- Fix bug: giving an all-zero initializer to "arima" could
  result in a crash
- Fix bug: the $ylist accessor was giving the wrong series
  ID in the case of "arima"
- Fix bug: VECM forecast failing in some cases
- Fix bug: panel plot, boxplots by group, was failing when the
  sample range begins at a positive offset
- Fix bug: "bundle-plot" mechanism for function packages in
  the GUI broken after the first invocation
- "mle": drop the requirement that a dataset is in place
- "foreign": support the changes in Julia version 1.0
- Windows: improve handling of non-ASCII filenames, including
  names not representable in the 8-bit code page
- Windows and Mac packages: update to gmp 6.1.2, mpfr 4.0.1
