Add another merge technique to smerge.
Add another merge technique to smerge.

bk: 3b978ef59ryaR0wctxQQqVwQEv1WwA
bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper