Log when -restrict-acl is in use.

Partly to reassure the user that they got what they asked for, and
partly so that's a clue for us in the logs when we get bug reports.

This involved repurposing platform_psftp_post_option_setup() (no longer
used since e22120fe) as platform_psftp_pre_conn_setup(), and moving it
to after logging is set up.

windows/window.c

@@ -840,6 +840,10 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
 	}
     }
 
+    if (restricted_acl) {
+	logevent(NULL, "Running with restricted process ACL");
+    }
+
     start_backend();
 
     /*