MDEV-6131 Unable to build Connector/ODBC 5.2.5 undefined reference to `my_charset_latin1'

Add charsets to the client API
(they are declared with MYSQL_PLUGIN_IMPORT, meaning the intention is to have them public)

libmysql/CMakeLists.txt

@@ -139,6 +139,10 @@ my_print_help
 
 SET(CLIENT_API_FUNCTIONS_5_5
 mysql_stmt_next_result
+# Charsets
+my_charset_bin
+my_charset_latin1
+my_charset_utf8_general_ci
 # Client plugins
 mysql_client_find_plugin
 mysql_client_register_plugin