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The canonical architecture is no longer checked when loading packages using a non-empty sub-architecture, since it is possible to (e.g.) build packages for i386-pc-linux-gnu on both that architecture and on x86_64-unknown-linux-gnu.
DF[i, j] failed in 2.6.0 if j was a logical vector selecting a single column.
Unix x11() would fail if a valid 'display' was specified but DISPLAY was unset. (PR#10379)