!apps: replace sclock_t with clock_t and drop redundant time_t/off_t casts

Align with the upstream nuttx change that drops the sclock_t alias now
that clock_t is itself a signed 64-bit type (int64_t).  Beyond the pure
sclock_t -> clock_t rename, this commit also removes the
now-unnecessary (time_t)-1 / (time_t)0 / (off_t)-1 casts that were
papering over the previously-unsigned time_t.

Files touched:

  - examples/alarm/alarm_main.c:        sclock_t -> clock_t
  - netutils/dhcpd/dhcpd.c:             sclock_t -> clock_t
  - netutils/ftpd/ftpd.c:               sclock_t -> clock_t
  - netutils/thttpd/libhttpd.c,
    netutils/thttpd/tdate_parse.c:      drop (time_t)-1 / (time_t)0 /
                                        (off_t)-1 sentinel casts
  - system/resmonitor/filldisk.c,
    system/zmodem/zm_receive.c:         sclock_t -> clock_t
  - testing/ostest/wdog.c:              sclock_t -> clock_t (the bulk
                                        of the rename, 30 sites)
  - testing/testsuites/kernel/syscall/cases/{clock_nanosleep_test,
    fsync_test,time_test}.c:            drop (time_t)-1 casts in the
                                        new signed-time_t world

No behavioural change.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

netutils/dhcpd/dhcpd.c

@@ -661,7 +661,7 @@ static inline bool dhcpd_parseoptions(void)
             if (optlen >= 6 && optlen < remaining)
               {
                 memcpy(&tmp, &ptr[DHCPD_OPTION_DATA], 4);
-                g_state.ds_optleasetime = (time_t)ntohl(tmp);
+                g_state.ds_optleasetime = ntohl(tmp);
               }
             break;
 

netutils/ftpd/ftpd.c

@@ -2305,11 +2305,11 @@ static int ftpd_listbuffer(FAR struct ftpd_session_s *session,
 
       /* time */
 
-      memcpy(&tm, localtime((FAR const time_t *)&st->st_mtime), sizeof(tm));
+      memcpy(&tm, localtime(&st->st_mtime), sizeof(tm));
       offset += snprintf(&buffer[offset], buflen - offset, " %s %2u",
                          g_monthtab[tm.tm_mon], tm.tm_mday);
       now = time(0);
-      if ((now - st->st_mtime) > (time_t)(60 * 60 * 24 * 180))
+      if (now - st->st_mtime > 60 * 60 * 24 * 180)
         {
           offset += snprintf(&buffer[offset], buflen - offset, " %5u",
                              tm.tm_year + 1900);

netutils/thttpd/libhttpd.c

@@ -327,7 +327,7 @@ static void send_mime(httpd_conn *hc, int status, const char *title,
           (hc->range_end >= hc->range_start) &&
           ((hc->range_end != length - 1) ||
            (hc->range_start != 0)) &&
-          (hc->range_if == (time_t) - 1 || hc->range_if == hc->sb.st_mtime))
+          (hc->range_if == -1 || hc->range_if == hc->sb.st_mtime))
         {
           partial_content = 1;
           status = 206;
@@ -340,7 +340,7 @@ static void send_mime(httpd_conn *hc, int status, const char *title,
         }
 
       gettimeofday(&now, NULL);
-      if (mod == (time_t)0)
+      if (mod == 0)
         {
           mod = now.tv_sec;
         }
@@ -510,7 +510,7 @@ static int send_err_file(httpd_conn *hc, int status, char *title,
     }
 
   send_mime(hc, status, title, "", extraheads, "text/html; charset=%s",
-            (off_t)-1, (time_t)0);
+            -1, 0);
   for (; ; )
     {
       nread = fread(buf, 1, sizeof(buf) - 1, fp);
@@ -2421,8 +2421,8 @@ int httpd_get_conn(httpd_server *hs, int listen_fd, httpd_conn *hc)
   hc->altdir[0]         = '\0';
 #endif
   hc->buflen = 0;
-  hc->if_modified_since = (time_t) - 1;
-  hc->range_if          = (time_t)-1;
+  hc->if_modified_since = -1;
+  hc->range_if          = -1;
   hc->contentlength     = -1;
   hc->type = "";
 #ifdef CONFIG_THTTPD_VHOST
@@ -2926,7 +2926,7 @@ int httpd_parse_request(httpd_conn *hc)
             {
               cp = &buf[18];
               hc->if_modified_since = tdate_parse(cp);
-              if (hc->if_modified_since == (time_t) - 1)
+              if (hc->if_modified_since == -1)
                 {
                   nerr("ERROR: unparsable time: %s\n", cp);
                 }
@@ -2973,7 +2973,7 @@ int httpd_parse_request(httpd_conn *hc)
             {
               cp = &buf[9];
               hc->range_if = tdate_parse(cp);
-              if (hc->range_if == (time_t) - 1)
+              if (hc->range_if == -1)
                 {
                   nerr("ERROR: unparsable time: %s\n", cp);
                 }
@@ -3521,7 +3521,7 @@ int httpd_start_request(httpd_conn *hc, struct timeval *nowp)
       send_mime(hc, 200, ok200title, hc->encodings, "", hc->type,
                 hc->sb.st_size, hc->sb.st_mtime);
     }
-  else if (hc->if_modified_since != (time_t) - 1 &&
+  else if (hc->if_modified_since != -1 &&
            hc->if_modified_since >= hc->sb.st_mtime)
     {
       send_mime(hc, 304, err304title, hc->encodings, "",

netutils/thttpd/tdate_parse.c

@@ -348,7 +348,7 @@ time_t tdate_parse(char *str)
 #endif /* Day of week not yet supported by NuttX */
   else
     {
-      return (time_t) - 1;
+      return -1;
     }
 
   if (tm.tm_year > 1900)