cleanup: LEX_USER::pwtext and LEX_USER::pwhash

Was:
* LEX_USER::password was storing sometimes
  plaintext password and sometimes password hash
* LEX_USER::auth was storing sometimes password hash and
  sometimes plugin authentication string

Now:
* LEX_USER::pwtext stores the password in plain-text
* LEX_USER::pwhash stores the password hash
* LEX_USER::auth stores the plugin authentication string

sql/sql_yacc.yy

@@ -15067,14 +15067,14 @@ opt_for_user:
         ;
 
 text_or_password:
-          TEXT_STRING { Lex->definer->auth= $1;}
-        | PASSWORD_SYM '(' TEXT_STRING ')' { Lex->definer->password= $3; }
+          TEXT_STRING { Lex->definer->pwhash= $1;}
+        | PASSWORD_SYM '(' TEXT_STRING ')' { Lex->definer->pwtext= $3; }
         | OLD_PASSWORD_SYM '(' TEXT_STRING ')'
           {
-            Lex->definer->password= $3;
-            Lex->definer->auth.str= Item_func_password::alloc(thd,
+            Lex->definer->pwtext= $3;
+            Lex->definer->pwhash.str= Item_func_password::alloc(thd,
                                    $3.str, $3.length, Item_func_password::OLD);
-            Lex->definer->auth.length=  SCRAMBLED_PASSWORD_CHAR_LENGTH_323;
+            Lex->definer->pwhash.length=  SCRAMBLED_PASSWORD_CHAR_LENGTH_323;
           }
         ;
 
@@ -15648,14 +15648,15 @@ using_or_as: USING | AS ;
 grant_user:
           user IDENTIFIED_SYM BY TEXT_STRING
           {
-            $$=$1; $1->password=$4;
+            $$= $1;
+            $1->pwtext= $4;
             if (Lex->sql_command == SQLCOM_REVOKE)
               MYSQL_YYABORT;
           }
         | user IDENTIFIED_SYM BY PASSWORD_SYM TEXT_STRING
           { 
             $$= $1; 
-            $1->auth= $5;
+            $1->pwhash= $5;
           }
         | user IDENTIFIED_SYM via_or_with ident_or_text
           {

sql/structs.h

@@ -202,7 +202,8 @@ extern const char *show_comp_option_name[];
 typedef int *(*update_var)(THD *, struct st_mysql_show_var *);
 
 typedef struct	st_lex_user {
-  LEX_STRING user, host, password, plugin, auth;
+  LEX_STRING user, host, plugin, auth;
+  LEX_STRING pwtext, pwhash;
   bool is_role() { return user.str[0] && !host.str[0]; }
   void set_lex_string(LEX_STRING *l, char *buf)
   {
@@ -213,8 +214,8 @@ typedef struct	st_lex_user {
   }
   void reset_auth()
   {
-    password.length= plugin.length= auth.length= 0;
-    password.str= 0;
+    pwtext.length= pwhash.length= plugin.length= auth.length= 0;
+    pwtext.str= pwhash.str= 0;
     plugin.str= auth.str= const_cast<char*>("");
   }
 } LEX_USER;