Implement post-MVP features and native stack overflow check (#243)

Implement native thread stack overflow check
Implement post-MVP: Non-trapping float-to-int conversions
Implement post-MVP: Sign-extension operators
Enhance WASM loader checks

core/shared/platform/include/platform_api_vmcore.h

@@ -65,6 +65,13 @@ uint64 os_time_get_boot_microsecond(void);
  */
 korp_tid os_self_thread(void);
 
+/**
+ * Get current thread's stack boundary address, used for runtime
+ * to check the native stack overflow. Return NULL if it is not
+ * easy to implement, but may have potential issue.
+ */
+uint8 *os_thread_get_stack_boundary(void);
+
 /**
  ************** mutext APIs ***********
  *  vmcore:  Not required until pthread is supported by runtime