[R] R 3.4.2 is released

[Duncan Murdoch]

I've just finished the Windows build of R 3.4.2.  It will make it to 
CRAN and its mirrors over the next few hours.

This is the last binary release that I will be producing.  I've been 
building them for about 15 years, and it's time to retire.  Builds using 
different tools and scripts are available from 
https://mran.microsoft.com/download/.  I'll be putting my own scripts on 
CRAN soon in case anyone wants to duplicate them.

Nightly builds of R-patched and R-devel will continue to run on 
autopilot for the time being, without maintenance.

I will also be retiring from maintenance of the Rtools collection.

Duncan Murdoch