Don't use sed -r; instead use old-style regexp
Rev d895158fe8af introduced some sed -r tests, but -r is only available on GNU
sed, while BSD sed uses -E. Better to use old-style regular expressions, that
way the tests work on all sed variants.
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a