[Rd] Updated Windows toolchain

[Prof Brian Ripley]

An updated toolchain is now being used for Windows' builds of R-devel: 
details are in the R-admin manual and at
http://www.murdoch-sutherland.com/Rtools/ and
http://www.stats.ox.ac.uk/pub/Rtools/

Both 32- and 64-bit parts of the toolchain use v2.0.1 of the Mingw-w64 
project's runtime and a beta of gcc 4.5.4: the Mingw.org project's 
builds are no longer used.  This should mean that code which compiles 
for 64-bit Windows also compiles for 32-bit Windows, and v.v. unless 
code makes (incorrect but common) assumptions that pointers fit into 
longs.

A very few packages will need modifications because they contain 
declarations which clash with the headers in this toolchain: where we 
are aware of problems the maintainers have been informed.

At DLL level different Windows' toolchains should be compatible: at C 
level they mostly are but at C++ level they are pretty much 
incompatible (so that for example GDAL has to be re-compiled for every 
toolchain: and Rcpp users need to be careful to use only one toolchain 
for Rcpp and their packages).  All the external software previously 
made available (and more) is made available at 
http://www.stats.ox.ac.uk/pub/Rtools .

The toolchain has support for OpenMP and pthreads: however OpenMP 
support is not enabled by default in R (it is too slow to be much 
use).  If you do make use of it in your packages, be aware that you 
will need to ship the appropriate pthreads DLL(s).

It is expected that there will be several further minor updates prior 
to the release of 2.15.0 in ca 4 months, but this step is the major 
one.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595