Expose utf8mb4_bin charset for plugins

Cleanup other linker errors

include/m_ctype.h

@@ -1175,7 +1175,7 @@ extern struct charset_info_st my_charset_utf8mb3_general_nopad_ci;
 extern struct charset_info_st my_charset_utf8mb3_general_mysql500_ci;
 extern struct charset_info_st my_charset_utf8mb3_unicode_ci;
 extern struct charset_info_st my_charset_utf8mb3_unicode_nopad_ci;
-extern struct charset_info_st my_charset_utf8mb4_bin;
+extern MYSQL_PLUGIN_IMPORT struct charset_info_st my_charset_utf8mb4_bin;
 extern struct charset_info_st my_charset_utf8mb4_general_ci;
 extern struct charset_info_st my_charset_utf8mb4_nopad_bin;
 extern struct charset_info_st my_charset_utf8mb4_general_nopad_ci;

plugin/type_mysql_json/mysql_json.h

@@ -41,4 +41,5 @@ enum JSONB_TYPES {
 
 bool parse_mysql_json_value(String *buffer, JSONB_TYPES type, const uchar *data,
                             size_t len, size_t depth);
+
 #endif  /* MYSQL_JSON_INCLUDED */

plugin/type_mysql_json/type.cc

@@ -21,7 +21,7 @@
 #include <mysqld_error.h>
 #include "mysql_json.h"
 
-static const LEX_CSTRING empty_clex_str= {"", 0};
+const LEX_CSTRING empty_clex_str= {"", 0};
 
 class Type_handler_mysql_json: public Type_handler_blob
 {

sql/sql_type.h

@@ -3498,7 +3498,7 @@ class Vers_type_timestamp: public Vers_type_handler
                         const Column_definition *row_start,
                         const Column_definition *row_end) const;
 };
-extern Vers_type_timestamp vers_type_timestamp;
+extern MYSQL_PLUGIN_IMPORT Vers_type_timestamp vers_type_timestamp;
 
 
 class Vers_type_trx: public Vers_type_handler