cleanup: add 'const' to password validation API

include/mysql/plugin_password_validation.h

@@ -42,8 +42,8 @@ struct st_mariadb_password_validation
     Function provided by the plugin which should perform password validation
     and return 0 if the password has passed the validation.
   */
-  int (*validate_password)(MYSQL_CONST_LEX_STRING *username,
-                           MYSQL_CONST_LEX_STRING *password);
+  int (*validate_password)(const MYSQL_CONST_LEX_STRING *username,
+                           const MYSQL_CONST_LEX_STRING *password);
 };
 
 #ifdef __cplusplus

include/mysql/plugin_password_validation.h.pp

@@ -531,6 +531,6 @@ void thd_wakeup_subsequent_commits(void* thd, int wakeup_error);
 struct st_mariadb_password_validation
 {
   int interface_version;
-  int (*validate_password)(MYSQL_CONST_LEX_STRING *username,
-                           MYSQL_CONST_LEX_STRING *password);
+  int (*validate_password)(const MYSQL_CONST_LEX_STRING *username,
+                           const MYSQL_CONST_LEX_STRING *password);
 };

plugin/cracklib_password_check/cracklib_password_check.c

@@ -21,7 +21,8 @@
 
 static char *dictionary;
 
-static int crackme(MYSQL_CONST_LEX_STRING *username, MYSQL_CONST_LEX_STRING *password)
+static int crackme(const MYSQL_CONST_LEX_STRING *username,
+                   const MYSQL_CONST_LEX_STRING *password)
 {
   char *user= alloca(username->length + 1);
   char *host;

plugin/simple_password_check/simple_password_check.c

@@ -22,8 +22,8 @@
 
 static unsigned min_length, min_digits, min_letters, min_others;
 
-static int validate(MYSQL_CONST_LEX_STRING *username,
-                    MYSQL_CONST_LEX_STRING *password)
+static int validate(const MYSQL_CONST_LEX_STRING *username,
+                    const MYSQL_CONST_LEX_STRING *password)
 {
   unsigned digits=0 , uppers=0 , lowers=0, others=0, length= (unsigned)password->length;
   const char *ptr= password->str, *end= ptr + length;