Isolated emscripten in new lib

lib/emscripten/emtests/test_i32_mul_precise.c

@@ -0,0 +1,19 @@
+/*
+ * 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>
+
+int main(int argc, char **argv) {
+  unsigned long d1 = 0x847c9b5d;
+  unsigned long q = 0x549530e1;
+  if (argc > 1000) {
+    q += argc;
+    d1 -= argc;
+  }  // confuse optimizer
+  printf("%lu\n", d1 * q);
+  return 0;
+}