Drop use of volatile
The only usage remaining is in subprojects (which we don’t control/don’t want to fork), in gbitlock (which I haven’t yet looked at), in UNIX signal handling and a few other appropriate places, and in some global debugging variables which it’s probably best are treated like they could change at any moment (I think?).
Signed-off-by: Philip Withnall email@example.com
Fixes: #600 (closed)