dbfixup: automatically create .dbf files

[mcmasterg]

.dbf files are used to group database enums together. For example, IOB has:

38_98 39_97 39_99,LIOB33.IOB_Y1.PULLTYPE.PULLDOWN

Which says that bits 38_98 39_97 39_99 form an enum group. Additionally, the tag LIOB33.IOB_Y1.PULLTYPE.PULLDOWN, a tag implicitly part of the group with no bits set, should also be included.

Noting the .rdb has:

LIOB33.IOB_Y1.PULLTYPE.KEEPER 39_97 39_99
LIOB33.IOB_Y1.PULLTYPE.NONE 39_97
LIOB33.IOB_Y1.PULLTYPE.PULLDOWN <0 candidates>
LIOB33.IOB_Y1.PULLTYPE.PULLUP 38_98 39_97

Which becomes this .db:

LIOB33.IOB_Y1.PULLTYPE.KEEPER !38_98 39_97 39_99
LIOB33.IOB_Y1.PULLTYPE.NONE !38_98 !39_99 39_97
LIOB33.IOB_Y1.PULLTYPE.PULLDOWN !39_99 !38_98 !39_97
LIOB33.IOB_Y1.PULLTYPE.PULLUP !39_99 38_98 39_97

I recently added utility function add_site_group_zero() to help streamline creating tags for these. This could be used to create some metadata that could be processed on the resulting .rdb (pre-dbfixup .db) to figure out where these groups are, which is essentially what I do.