Comment # 21 on bug 126 from Johannes Pfau

I've implemented __builtin_volatile_load/store in
https://github.com/D-Programming-GDC/GDC/pull/82

with a DMD compatible API. (so volatileLoad/Store in core.bitop can be a simple
alias AFAICS)

I tested this and it should work and produce efficient code, but some feedback
would be appreciated :-)