Comment # 3 on bug 167 from Johannes Pfau

Yes, I hit this issue with 8bit AVRs (pointers/size_t is 16 bit on AVR although
registers are 8bit). Maybe a clean solution is to split Target::init /
Target::init2 and use Target::sizetsize in Type::init? However, overwriting
Type::tsize_t seems to work for now.

A related question: in d-codegen.cc::build_offset
tree ofs = fold_convert (Type::tsize_t->toCtype(), byte_offset);

shouldn't this use tptrdiff_t? I think this code could break if wordsize and
pointer size are different.
However, simply changing this to tptrdiff_t breaks the build. I guess we'd
really need a unsigned tptrdiff_t.