Import reference-types feature (#612)

Implement spec reference-types proposal for interpreter, AOT and JIT, update documents and add sample. And upgrade AOT_CURRENT_VERSION to 3 as AOT file format and AOT module instance layout are changed.

Signed-off-by: Wenyong Huang <wenyong.huang@intel.com>

core/iwasm/interpreter/wasm_loader.h

@@ -70,6 +70,14 @@ wasm_loader_find_block_addr(BlockAddr *block_addr_cache,
                             uint8 **p_else_addr,
                             uint8 **p_end_addr);
 
+#if WASM_ENABLE_REF_TYPES != 0
+void
+wasm_set_ref_types_flag(bool enable);
+
+bool
+wasm_get_ref_types_flag();
+#endif
+
 #ifdef __cplusplus
 }
 #endif