Add --reload option to sesman

Adds a --reload switch to sesman and plumbs this in
to systemctl reload xrdp-sesman.service

common/os_calls.c

@@ -3043,6 +3043,18 @@ g_sigterm(int pid)
 #endif
 }
 
+/*****************************************************************************/
+/* does not work in win32 */
+int
+g_sighup(int pid)
+{
+#if defined(_WIN32)
+    return 0;
+#else
+    return kill(pid, SIGHUP);
+#endif
+}
+
 /*****************************************************************************/
 /* returns 0 if ok */
 /* the caller is responsible to free the buffs */