swift234

Updated to prototype as discussed yesterday.  Added substring function.  I currently have the data null-terminated, except when created by substring, just to aid in I/O.  It will be easy to strip the trailing null off.  It is not currently counted in the size() or size_bytes() observers.  Though not complete, this prototype is looking promising to me.  Problem area:  On 32 bit platforms I don't have robust storage for the bit that says whether or not the char* is owned.  I'm currently using the high bit of the pointer.  I note that when the pointer is not owned (it points into rom), it is 1-byte aligned, making the use of the low order bit problematic.

Swift SVN r448