Enable WASI feature, enhance security and add SGX sample (#142)

Change emcc to clang
Refine interpreter to improve perforamnce

core/shared-lib/platform/alios/bh_platform.c

@@ -4,14 +4,20 @@
  */
 
 #include "bh_platform.h"
+#include "bh_common.h"
 #include <stdlib.h>
 #include <string.h>
 
 char *bh_strdup(const char *s)
 {
+    uint32 size;
     char *s1 = NULL;
-    if (s && (s1 = bh_malloc(strlen(s) + 1)))
-        memcpy(s1, s, strlen(s) + 1);
+
+    if (s) {
+        size = (uint32)(strlen(s) + 1);
+        if ((s1 = bh_malloc(size)))
+            bh_memcpy_s(s1, size, s, size);
+    }
     return s1;
 }