MDEV-7419 Function cli_safe_read not exported

Start the client API for low-level protocol access:
* unsigned long mysql_net_read_packet(MYSQL *mysql);
* unsigned long mysql_net_field_length(unsigned char **packet);

include/mysql.h

@@ -854,6 +854,12 @@ my_socket STDCALL mysql_get_socket(const MYSQL *mysql);
 unsigned int STDCALL mysql_get_timeout_value(const MYSQL *mysql);
 unsigned int STDCALL mysql_get_timeout_value_ms(const MYSQL *mysql);
 
+/********************************************************************
+  mysql_net_ functions - low-level API to MySQL protocol
+*********************************************************************/
+unsigned long STDCALL mysql_net_read_packet(MYSQL *mysql);
+unsigned long STDCALL mysql_net_field_length(unsigned char **packet);
+
 /* status return codes */
 #define MYSQL_NO_DATA        100
 #define MYSQL_DATA_TRUNCATED 101

include/mysql.h.pp

@@ -732,3 +732,5 @@ int mysql_close_cont(MYSQL *sock, int status);
 my_socket mysql_get_socket(const MYSQL *mysql);
 unsigned int mysql_get_timeout_value(const MYSQL *mysql);
 unsigned int mysql_get_timeout_value_ms(const MYSQL *mysql);
+unsigned long mysql_net_read_packet(MYSQL *mysql);
+unsigned long mysql_net_field_length(unsigned char **packet);

libmysql/CMakeLists.txt

@@ -238,6 +238,9 @@ dynamic_column_get
 dynamic_column_prepare_decimal
 #
 mariadb_deinitialize_ssl
+# low-level API to MySQL protocol
+mysql_net_read_packet
+mysql_net_field_length
 )
 
 SET(CLIENT_API_FUNCTIONS

libmysql/libmysql.c

@@ -4897,3 +4897,20 @@ my_bool STDCALL mysql_read_query_result(MYSQL *mysql)
   return (*mysql->methods->read_query_result)(mysql);
 }
 
+/********************************************************************
+  mysql_net_ functions - low-level API to MySQL protocol
+*********************************************************************/
+#if MYSQL_VERSION_ID > 100100
+#error remove these wrappers in 10.1, rename functions instead
+#endif
+
+ulong STDCALL mysql_net_read_packet(MYSQL *mysql)
+{
+  return cli_safe_read(mysql);
+}
+
+ulong STDCALL mysql_net_field_length(uchar **packet)
+{
+  return net_field_length(packet);
+}
+