atomic.h: Add C11 <stdatomic.h> implementation
atomic.h
The implementation is only active if HAVE_STDATOMIC_H is defined, and only after the compiler fails to match all currently supported systems.
HAVE_STDATOMIC_H
atomic.h
: Add C11 <stdatomic.h> implementationThe implementation is only active if
HAVE_STDATOMIC_H
is defined,and only after the compiler fails to match all currently supported
systems.