This blog is updated daily.
A general description is here.
The included configuration code for 'libintl' has been updated to that from 'gettext' version 0.19.5.1 - this should only affect how an external library is detected. (Wish of PR#16464.)
(Windows) Compatibility information has been added to the manifests for 'Rgui.exe', 'Rterm.exe' and 'Rscript.exe'. This should allow 'win.version()' and 'Sys.info()' to report the actual Windows version up to Windows 10.
Some recently-added Windows time zone names have been added to the conversion table used to convert these to Olson names. (Including those relating to changes for Russia in Oct 2014, as in PR#16503.)
Windows '"wininet"' FTP first tries EPSV / PASV mode rather than only using active mode (reported by Dan Tenenbaum).
'close()' now reports the status of a 'pipe()' connection opened with an explicit 'open' argument. (PR#16481)
'detach()'ing the 'methods' package keeps '.isMethodsDispatchOn()' true, as long as the methods namespace is not unloaded.
It is now easier to use secure downloads from 'https://' URLs on builds which support them: no longer do non-default options need to be selected to do so. In particular, packages can be installed from repositories which offer 'https://' URLs, and those listed by 'setRepositories()' now do so (for some of their mirrors).
Support for 'https://' URLs is available on Windows, and on other platforms if support for 'libcurl' was compiled in and if that supports the 'https' protocol (system installations can be expected to do). So 'https://' support can be expected except on rather old OSes (an example being OS X 'Snow Leopard', where a non-system version of 'libcurl' can be used).
(Windows only) The default method for accessing URLs _via_ 'download.file()' and 'url()' has been changed to be '"wininet"' using Windows API calls. This changes the way proxies need to be set and security settings made: there have been some reports of 'ftp:' sites being inaccessible under the new default method (but the previous methods remain available).
(Windows only) 'setInternet2(TRUE)' is now the default. The command-line option '--internet2' and environment variable 'R_WIN_INTERNET2' are now ignored.
Thus by default the '"internal"' method for 'download.file()' and 'url()' uses the '"wininet"' method: to revert to the previous default use 'setInternet2(FALSE)'.
This means that 'https://' URLs can be read by default by 'download.file()' (they have been readable by 'file()' and 'url()' since R 3.2.0).
There are implications for how proxies need to be set (see '?download.file').