Removed uncontext.h.
This removal was missed the changeset
#if (NXT_MACOSX)
-#define _XOPEN_SOURCE /* ucontext(3). */
#ifndef _DARWIN_C_SOURCE
#define _DARWIN_C_SOURCE /* pthread_threadid_np(), mach_port_t. */
#endif
#endif
#include <sys/wait.h>
#include <time.h>
-#include <ucontext.h>
#include <unistd.h>
#include <pthread.h>
