Add FCTX_ATTR_CLR and FCTX_ATTR_SET macros (v9_11)
master and v9_14 have FCTX_ATTR_CLR and FCTX_ATTR_SET. Add non atomic versions to v9_11 to aid back porting.
#define FCTX_ATTR_SET(f, a) atomic_fetch_or_release(&(f)->attributes, (a))
#define FCTX_ATTR_CLR(f, a) atomic_fetch_and_release(&(f)->attributes, ~(a))