[phobos] sizediff_t

[Andrei Alexandrescu]

One question - we don't have a type for the difference of two size_t 
objects. That would be int on m32 and long on m64. C has historically 
used ptrdiff_t for that, but not all size differences are pointer 
differences, so gnu has acknowledged that by defining ssize_t ("signed 
size_t" I suppose).

While being in a crunch making some 64-bit changes I defined the type 
sizediff_t. I wonder if that's okay as a permanent solution.


Andrei