move authentication_windows_client and mysql_clear_password clear client auth plugins

out of libmysql into separate dynamic plugins in the plugin/ directory.

move dialog and auth_socket plugins out of the plugin directory with examples into
dedicated directories in plugin/

include/mysql/auth_dialog_client.h

@@ -0,0 +1,56 @@
+#ifndef MYSQL_AUTH_DIALOG_CLIENT_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
+
+  Definitions needed to use Dialog client authentication plugin
+*/
+
+struct st_mysql;
+
+#define MYSQL_AUTH_DIALOG_CLIENT_INCLUDED
+
+/**
+  type of the mysql_authentication_dialog_ask function
+
+  @param mysql          mysql
+  @param type           type of the input
+                        1 - ordinary string input
+                        2 - password string
+  @param prompt         prompt
+  @param buf            a buffer to store the use input
+  @param buf_len        the length of the buffer
+
+  @retval               a pointer to the user input string.
+                        It may be equal to 'buf' or to 'mysql->password'.
+                        In all other cases it is assumed to be an allocated
+                        string, and the "dialog" plugin will free() it.
+*/
+typedef char *(*mysql_authentication_dialog_ask_t)(struct st_mysql *mysql,
+                      int type, const char *prompt, char *buf, int buf_len);
+
+/**
+  first byte of the question string is the question "type".
+  It can be an "ordinary" or a "password" question.
+  The last bit set marks a last question in the authentication exchange.
+*/
+#define ORDINARY_QUESTION       "\2"
+#define LAST_QUESTION           "\3"
+#define PASSWORD_QUESTION       "\4"
+#define LAST_PASSWORD           "\5"
+
+#endif