llist: Add a C++ wrapper for linux_list

This commit adds the LListHead class which is a wrapper around the
linuxlist. It adds an additional member to refer to the container,
since the container_of macro doesn't work properly with C++ classes.
All functions and macros from linuxlist.h are support except for the
entry macros (e.g. llist_entry, llist_for_each_entry, ...). To access
the container (entry), an entry() method is provided instead:

  llist_for_each(pos, &elems) {
      pos->entry()->do_something();
  }

Sponsored-by: On-Waves ehf
diff --git a/tests/llist/LListTest.cpp b/tests/llist/LListTest.cpp
new file mode 100644
index 0000000..04f741c
--- /dev/null
+++ b/tests/llist/LListTest.cpp
@@ -0,0 +1,87 @@
+/*
+ * LListTest.cpp
+ *
+ * Copyright (C) 2015 by Sysmocom s.f.m.c. GmbH
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "cxx_linuxlist.h"
+
+extern "C" {
+#include <osmocom/core/application.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/utils.h>
+}
+
+#include <errno.h>
+
+
+struct TestElem {
+	const char *str;
+	LListHead<TestElem> list;
+
+	TestElem(const char *s) : str(s), list(this) {};
+};
+
+static void test_linux_list()
+{
+	LListHead<TestElem> elems, *pos, *tmp;
+	TestElem elem1("number one");
+	TestElem elem2("number two");
+	TestElem elem3("number three");
+	int count = 0;
+
+	printf("=== start %s ===\n", __func__);
+
+	llist_add_tail(&elem1.list, &elems);
+	llist_add_tail(&elem2.list, &elems);
+	llist_add_tail(&elem3.list, &elems);
+
+	llist_for_each(pos, &elems) {
+		count += 1;
+		printf(" %i -> %s\n", count, pos->entry()->str);
+	}
+	OSMO_ASSERT(count == 3);
+
+	count = 0;
+	llist_for_each_safe(pos, tmp, &elems) {
+		count += 1;
+		if (count == 2)
+			llist_del(pos);
+
+		printf(" %i -> %s\n", count, pos->entry()->str);
+	}
+	OSMO_ASSERT(count == 3);
+
+	count = 0;
+	llist_for_each(pos, &elems) {
+		count += 1;
+		OSMO_ASSERT(pos != &elem2.list);
+		printf(" %i -> %s\n", count, pos->entry()->str);
+	}
+	OSMO_ASSERT(count == 2);
+
+	printf("=== end %s ===\n", __func__);
+}
+
+int main(int argc, char **argv)
+{
+	test_linux_list();
+
+	return EXIT_SUCCESS;
+}