/* man pages claim that the third argument is a sigcontext struct,
but ucontext_t is defined, matches sigcontext where sensible,
offers better access to mcontext, and is of course the SUSv2-
/* man pages claim that the third argument is a sigcontext struct,
but ucontext_t is defined, matches sigcontext where sensible,
offers better access to mcontext, and is of course the SUSv2-