Ability to name/address bitfields

[Importing from RubyForge]

It would be nice to be able to assign identifiers to individual bits or ranges of bits:

bs = BitString.new(0, 32)
bs.name(0..2, 'severity')
bs.name(3..15, 'msgid')
bs.name(0, :successful)

bs[:msgid] = 23
bs[:severity] = 3
bs[:successful] = false  # true/false for bit values is a separate FREQ
