[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 
and R 4.3, is available as revision 5948 from

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

This update adds grpc, re2, abseil, c-ares. It includes a major update 
of protobuf and ships with protoc. There are some improvements in 
pkg-config wrappers.

Some software using xml2 may have to be updated to the new API.

Software linking protobuf and httpuv now has to link additional 
dependencies.

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

Best
Tomas