[PATCH v2] Add and use new glibc-internal futex API.

[Roland McGrath]

> Those types imply seq_cst memory order for plain loads and stores, which 
> isn't what's wanted in most places in glibc (one might expect many places 
> presently using plain loads and stores actually want relaxed memory 
> order).  Operations on _Atomic types may also bring in libatomic 
> dependencies depending on processor support, causing obvious problems with 
> circular dependencies (libatomic depends on libpthread).

OK.  I guess we'll have to go with our own typedef names when we clean this up.