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R CMD build tries harder to clean up the inst/doc directory from the remnants of earlier builds.
It also removes any directories with extension .Rcheck.
Use of strwidth/height(units="user") (the default) is again an error before a user coordinate system has been set on the device, rather than giving nonsensical values (the effect of r31367).
Rare string width calculations in package grid were not interpreting the string encoding correctly.
is() was wrong for some S3 class objects with multi-string classclass for length greater than one.