merge r3473, r3474, r3385, r3386, r3537: signal processing stability: *) use sys_errlist[] in signal handler instead of non Async-Signal-Safe strerror_r() *) do not update time in the timer signal handler, since localtime_r() is not Async-Signal-Safe function *) use previously cached GMT offset value to update time from a signal handler *) change ngx_time_update() interface since there are no notification methods those return time *) introduce ngx_time_sigsafe_update() to update the error log time only *) change ngx_time_update() interface

--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -1128,7 +1128,7 @@ ngx_http_file_cache_manager_sleep(ngx_ht
 
     if (cache->files++ > 100) {
 
-        ngx_time_update(0, 0);
+        ngx_time_update();
 
         elapsed = ngx_abs((ngx_msec_int_t) (ngx_current_msec - cache->last));
 
@@ -1145,7 +1145,7 @@ ngx_http_file_cache_manager_sleep(ngx_ht
 
             ngx_msleep(200);
 
-            ngx_time_update(0, 0);
+            ngx_time_update();
         }
 
         cache->last = ngx_current_msec;