Isolated emscripten in new lib

lib/emscripten/emtests/test_vprintf.c

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2016 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 <stdarg.h>
+
+void print(const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  vprintf(format, args);
+  va_end(args);
+}
+
+int main() {
+  print("Call with %d variable argument.\n", 1);
+  print("Call with %d variable %s.\n", 2, "arguments");
+
+  return 0;
+}