util: silence conversion warnings

timeval::tv_usec might be a 32-bit integer and timespec::tv_nsec might
be a 64-bit integer. This is the case when building for recent macOS
versions, for example. Just treat tv_usec as an int, which should
hopefully always be sufficient on systems with
`HAVE_CLOCK_GETTIME_MONOTONIC`.

Closes https://github.com/curl/curl/pull/5695

src/tool_util.c

@@ -74,7 +74,7 @@ struct timeval tvnow(void)
   struct timespec tsnow;
   if(0 == clock_gettime(CLOCK_MONOTONIC, &tsnow)) {
     now.tv_sec = tsnow.tv_sec;
-    now.tv_usec = tsnow.tv_nsec / 1000;
+    now.tv_usec = (int)(tsnow.tv_nsec / 1000);
   }
   /*
   ** Even when the configure process has truly detected monotonic clock

tests/libtest/testutil.c

@@ -55,7 +55,7 @@ struct timeval tutil_tvnow(void)
   struct timespec tsnow;
   if(0 == clock_gettime(CLOCK_MONOTONIC, &tsnow)) {
     now.tv_sec = tsnow.tv_sec;
-    now.tv_usec = tsnow.tv_nsec / 1000;
+    now.tv_usec = (int)(tsnow.tv_nsec / 1000);
   }
   /*
   ** Even when the configure process has truly detected monotonic clock

tests/server/util.c

@@ -475,7 +475,7 @@ static struct timeval tvnow(void)
   struct timespec tsnow;
   if(0 == clock_gettime(CLOCK_MONOTONIC, &tsnow)) {
     now.tv_sec = tsnow.tv_sec;
-    now.tv_usec = tsnow.tv_nsec / 1000;
+    now.tv_usec = (int)(tsnow.tv_nsec / 1000);
   }
   /*
   ** Even when the configure process has truly detected monotonic clock