update connector document

documentation/webdocs/markdowndocs/Connector.md

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 TDengine provides many connectors for development, including C/C++, JAVA, Python, RESTful, Go, Node.JS, etc.
 
+NOTE: All APIs which require a SQL string as parameter, including but not limit to `taos_query`, `taos_query_a`, `taos_subscribe` in the C/C++ Connector and their counterparts in other connectors, can ONLY process one SQL statement at a time. If more than one SQL statements are provided, their behaviors are undefined.
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 ## C/C++ API
 
 C/C++ APIs are similar to the MySQL APIs. Applications should include TDengine head file _taos.h_ to use C/C++ APIs by adding the following line in code:

documentation/webdocs/markdowndocs/connector-ch.md

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 TDengine提供了丰富的应用程序开发接口，其中包括C/C++、JAVA、Python、RESTful、Go等，便于用户快速开发应用。
 
+注意：所以执行 SQL 语句的 API，例如 C/C++ Connector 中的 `tao_query`、`taos_query_a`、`taos_subscribe` 等，以及其它语言中与它们对应的API，每次都只能执行一条 SQL 语句，如果实际参数中包含了多条语句，它们的行为是未定义的。
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 ## C/C++ Connector
 
 C/C++的API类似于MySQL的C API。应用程序使用时，需要包含TDengine头文件 _taos.h_（安装后，位于 _/usr/local/taos/include_）：