[R-SIG-Win] Rtools43 update

[Tomas Kalibera]

Dear R Windows developers,

an update of Rtools43, the toolchain for R for Windows used by R-devel, 
is now available as revision 5550 from

https://cran.r-project.org/bin/windows/Rtools/rtools43/rtools.html

In addition to updates to the included libraries, the installer now uses 
a three-element version (4.3.5550) instead of previously used only two 
elements (4.3). This makes it easier to see which version is installed 
in "Add/Remove Programs" and it may also impact third party tools for 
installing software on Windows.

Updates of curl and webp require changes in the list of libraries for 
linking.

See https://cran.r-project.org/bin/windows/Rtools/rtools43/news.html for 
more details.

Best
Tomas