Make printing AbstractBitVector1 more generic

[jlapeyre]

This line

Bits.jl/src/Bits.jl

Line 412 in 6f318ae

l = v isa BitVector1 ? lastactualpos(v.x) : v.len

Only supports current subtypes. I made a subtype that stores length in a different way. Using this line:

l = v isa BitVector1 ? lastactualpos(v.x) : length(v)

would make it more generic. Better yet would be something like:

printlength(v::Bits.BitVector1) = Bits.lastactualpos(v.x)
printlength(v) = length(v)

And then

l = printlength(v)