Do not assume time_t is long.

time_t is long on some platforms but not on all.
This plagues a warning on FreeBSD.

Taken from: Jung-uk Kim

(cherry picked from commit 1c030e28)

shell/source/unix/sysshell/recently_used_file_handler.cxx

@@ -91,11 +91,11 @@ namespace /* private */ {
 
         void set_timestamp(const string_t& character)
         {
-            time_t t;
+            long t;
             if (sscanf(character.c_str(), "%ld", &t) != 1)
                 timestamp_ = -1;
             else
-                timestamp_ = t;
+                timestamp_ = static_cast<time_t>(t);
         }
 
         void set_is_private(SAL_UNUSED_PARAMETER const string_t& /*character*/)