mescc: Support bash: Add sigdelset stub.

* lib/stub/sigdelset.c (sigdelset): New stub.
* lib/libc+gnu.c: Include it.

lib/libc+gnu.c

@@ -117,4 +117,5 @@
 // bash
 #include <stub/getpwuid.c>
 #include <stub/rand.c>
+#include <stub/sigdelset.c>
 #include <stub/ttyname.c>

lib/stub/sigdelset.c

@@ -0,0 +1,28 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libmes.h>
+#include <signal.h>
+
+int
+sigdelset (sigset_t *set, int signum)
+{
+  return 0;
+}