BASE91 - Fast Base-91 Encoder/Decoder Functions

[Dav]

I checked it out, Jack. On my other versions I had nbits = 0 defined, but removed it when tidying up the code I guess.  Good news is it didn't matter because nbits is worth zero when first being used, so the functions work.  I will fix the code to assign nbits though, because it is proper coding.

Using OPTION _EXPLICIT would help my coding a lot I think, maybe a good New Years resolution for me is to start using it, would prevent a lot of mistakes I often make.  

- Dav