rename ANYOF_UNICODE to ANYOF_NONBITMAP

rename ANYOF_UNICODE to ANYOF_NONBITMAP

I am about the hone the meaning of this to mean that there is something
outside the bitmap that is matchable by the node, and the new name
reflects that more accurately.

I am not retaining the old name because I'm about to remove it from the
flags field to save a bit and avoid masking operations, and any code
that would be using it would break at that point.