Some function in bitstringSyntax are now based on Arbnum.num instead of Int.int.

The old versions were vulnerable to Overflow exceptions.

Add a bit-string rotate operation.

Add a few more functions to bitstringSyntax.

Add a theory of bit-strings, which defines word operations over ``:bool list``. The maps "v2w" and "w2v" provide a connection to fixed-width bit vectors.