[phobos] std.string.cmp

[Brad Roberts]

Hrm.. I think I'd like to object to today's change of std.string.cmp to return
sizediff_t rather than int.  The reason.. Object.opCmp returns int.  So, using
cmp is needlessly painful.  A simple cast is dangerous.. consider what happens
if some how the cmp returns a multiple of 2^32.  But I guarantee that a simple
cast is what most people that run into the mismatch will do.

Thoughts?