Refactor time_* into nstime_*.

Use a single uint64_t in nstime_t to store nanoseconds rather than using
struct timespec.  This reduces fragility around conversions between long
and uint64_t, especially missing casts that only cause problems on
32-bit platforms.

test/include/test/jemalloc_test.h.in

@@ -94,7 +94,7 @@
 #  define JEMALLOC_H_STRUCTS
 #  define JEMALLOC_H_EXTERNS
 #  define JEMALLOC_H_INLINES
-#  include "jemalloc/internal/time.h"
+#  include "jemalloc/internal/nstime.h"
 #  include "jemalloc/internal/util.h"
 #  include "jemalloc/internal/qr.h"
 #  include "jemalloc/internal/ql.h"

test/include/test/timer.h

@@ -4,8 +4,8 @@
 #include <sys/time.h>
 
 typedef struct {
-	struct timespec t0;
-	struct timespec t1;
+	nstime_t t0;
+	nstime_t t1;
 } timedelta_t;
 
 void	timer_start(timedelta_t *timer);