pluggable auth with plugin examples

Makefile.am:
  add new API files to the check_abi rule,
  remove duplicates
client/CMakeLists.txt:
  now a client can use dlopen too
client/Makefile.am:
  be csh-friendly
include/my_global.h:
  add dummy plugs for dlopen and co.
  for the code that needs them to work in static builds
mysys/Makefile.am:
  be csh-friendly
plugin/auth/dialog.c:
  typo fixed

include/mysql/plugin_auth.h

@@ -0,0 +1,83 @@
+#ifndef MYSQL_PLUGIN_AUTH_INCLUDED
+/* Copyright (C) 2010 Sergei Golubchik and Monty Program Ab
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+/**
+  @file
+
+  Authentication Plugin API.
+
+  This file defines the API for server authentication plugins.
+*/
+
+#define MYSQL_PLUGIN_AUTH_INCLUDED
+
+#include <mysql/plugin.h>
+
+#define MYSQL_AUTHENTICATION_INTERFACE_VERSION 0x0100
+
+#include <mysql/plugin_auth_common.h>
+
+/**
+  Provides server plugin access to authentication information
+*/
+typedef struct st_mysql_server_auth_info
+{
+  /**
+    User name as sent by the client and shown in USER().
+    NULL if the client packet with the user name was not received yet.
+  */
+  const char *user_name;
+  /**
+    A corresponding column value from the mysql.user table for the
+    matching account name
+  */
+  const char *auth_string;
+
+  /**
+    Matching account name as found in the mysql.user table.
+    A plugin can override it with another name that will be
+    used by MySQL for authorization, and shown in CURRENT_USER()
+  */
+  char authenticated_as[MYSQL_USERNAME_LENGTH+1]; 
+  /**
+    This only affects the "Authentication failed. Password used: %s"
+    error message. If set, %s will be YES, otherwise - NO.
+    Set it as appropriate or ignore at will.
+  */
+  int  password_used;
+} MYSQL_SERVER_AUTH_INFO;
+
+/**
+  Server authentication plugin descriptor
+*/
+struct st_mysql_auth
+{
+  int interface_version;                        /**< version plugin uses */
+  /**
+    A plugin that a client must use for authentication with this server
+    plugin. Can be NULL to mean "any plugin".
+  */
+  const char *client_auth_plugin;
+  /**
+    Function provided by the plugin which should perform authentication (using
+    the vio functions if necessary) and return 0 if successful. The plugin can
+    also fill the info.authenticated_as field if a different username should be
+    used for authorization.
+  */
+  int (*authenticate_user)(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info);
+};
+#endif
+