Isolated emscripten in new lib

lib/emscripten/emtests/test_demangle_stacks_noassert.cpp

@@ -0,0 +1,26 @@
+// Copyright 2018 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <stdio.h>
+#include <stdlib.h>
+
+namespace NameSpace {
+class Class {
+ public:
+  __attribute__((noinline))
+  void Aborter(double x, char y, int *z) {
+    volatile int w = 1;
+    if (w) {
+      abort();
+    }
+  }
+};
+}
+
+int main(int argc, char **argv) {
+  NameSpace::Class c;
+  c.Aborter(1.234, 'a', NULL);
+  return 0;
+}