Isolated emscripten in new lib

lib/emscripten/emtests/test_i64_llabs.c

@@ -0,0 +1,14 @@
+/*
+ * 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 <stdlib.h>
+
+int main(int argc, char** argv) {
+  printf("%lld,%lld\n", llabs(-576460752303423489), llabs(576460752303423489));
+  return 0;
+}