This is, unfortunately, a limitation of The Way The World Works; either
we bite the bullet, make long the 64 bit type, and watch code break or
be slow on the 32 bit platforms, or we *cannot* offer a conforming
C implementation, and code is not obliged to try to support us.  (Although
I'd like to see Tcl work with our offsets, as long as no standard format
string can be used, it's Our Own Damn Fault (TM).)

-s