external: update backward-cpp to v1.4

rename the directory name to backward-cpp

Closes: #803
Signed-off-by: Shengjing Zhu <i@zhsj.me>

external/backward-cpp/test/stacktrace.cpp

@@ -0,0 +1,65 @@
+/*
+ * test/stacktrace.cpp
+ * Copyright 2013 Google Inc. All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "backward.hpp"
+#include <cstdio>
+#include "test/test.hpp"
+
+using namespace backward;
+
+void collect_trace(StackTrace& st) {
+	st.load_here();
+}
+
+TEST (minitrace) {
+	StackTrace st;
+	collect_trace(st);
+
+	Printer printer;
+	printer.print(st, stdout);
+}
+
+void d(StackTrace& st) {
+	st.load_here();
+}
+
+void c(StackTrace& st) {
+	return d(st);
+}
+
+void b(StackTrace& st) {
+	return c(st);
+}
+
+__attribute__ ((noinline))
+void a(StackTrace& st) {
+	return b(st);
+}
+
+TEST (smalltrace) {
+	StackTrace st;
+	a(st);
+
+	Printer printer;
+	printer.print(st, stdout);
+}