Fix a problem with the CVS import code that can result in two seperate files having duplicate delta keys if RCS files are duplicated in the  CVS repository.
Fix a problem with the CVS import code that can result in two seperate
files having duplicate delta keys if RCS files are duplicated in the 
CVS repository.

bk: 412a5b61BFxZtOGlYcaCkyjBUacUVQ
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