Fix a bug in smerge.c where in fails to merge correctly for certain line  lengths.
Fix a bug in smerge.c where in fails to merge correctly for certain line 
lengths.

bk: 3bab5efeeM4JswsUqts4dfP7HZPPQA
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