Add shared heap sample (#3806)

samples/shared-heap/wasm-apps/test1.c

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+
+extern void *
+shared_malloc(uint32_t size);
+extern void
+shared_free(void *ptr);
+
+void *
+my_shared_malloc(uint32_t size, uint32_t index)
+{
+    char *buf = shared_malloc(size);
+
+    if (buf)
+        snprintf(buf, 1024, "Hello, this is buf %u allocated from shared heap",
+                 index);
+
+    return buf;
+}
+
+void
+my_shared_free(void *ptr)
+{
+    shared_free(ptr);
+}