unix, windows: make uv_now() return uint64_t

Using int64_t doesn't make sense here because the return value is never
negative.

include/uv-private/uv-win.h

@@ -277,7 +277,7 @@ RB_HEAD(uv_timer_tree_s, uv_timer_s);
     /* The loop's I/O completion port */                                      \
   HANDLE iocp;                                                                \
   /* The current time according to the event loop. in msecs. */               \
-  int64_t time;                                                               \
+  uint64_t time;                                                              \
   /* Tail of a single-linked circular queue of pending reqs. If the queue */  \
   /* is empty, tail_ is NULL. If there is only one item, */                   \
   /* tail_->next_req == tail_ */                                              \

include/uv.h

@@ -266,7 +266,7 @@ UV_EXTERN void uv_ref(uv_handle_t*);
 UV_EXTERN void uv_unref(uv_handle_t*);
 
 UV_EXTERN void uv_update_time(uv_loop_t*);
-UV_EXTERN int64_t uv_now(uv_loop_t*);
+UV_EXTERN uint64_t uv_now(uv_loop_t*);
 
 /*
  * Get backend file descriptor. Only kqueue, epoll and event ports are

src/unix/core.c

@@ -306,7 +306,7 @@ void uv_update_time(uv_loop_t* loop) {
 }
 
 
-int64_t uv_now(uv_loop_t* loop) {
+uint64_t uv_now(uv_loop_t* loop) {
   return loop->time;
 }
 

src/win/timer.c

@@ -45,7 +45,7 @@ void uv_update_time(uv_loop_t* loop) {
 }
 
 
-int64_t uv_now(uv_loop_t* loop) {
+uint64_t uv_now(uv_loop_t* loop) {
   return loop->time;
 }
 

test/test-timer-again.c

@@ -31,7 +31,7 @@ static int repeat_2_cb_allowed = 0;
 
 static uv_timer_t dummy, repeat_1, repeat_2;
 
-static int64_t start_time;
+static uint64_t start_time;
 
 
 static void close_cb(uv_handle_t* handle) {

test/test-timer.c

@@ -29,7 +29,7 @@ static int repeat_cb_called = 0;
 static int repeat_close_cb_called = 0;
 static int order_cb_called = 0;
 
-static int64_t start_time;
+static uint64_t start_time;
 
 
 static void once_close_cb(uv_handle_t* handle) {