Cleanup of unused variables.

Fixed "discover" in the handler API.

Fixed problem where handlerton was not zero'ed. I need to look around, I suspect this problem is more widespread. 


sql/ha_innodb.h:
  Unused variable
sql/ha_ndbcluster.cc:
  Added "discover" to handlerton.
sql/handler.cc:
  Added plugin loop and correctly now use handler API.
sql/handler.h:
  Removed unused variable. Added discover to handler API
sql/mysqld.cc:
  Removed unused variables.
sql/sql_plugin.cc:
  Fixed DBUG Enter comment (obvious cut paste mistake)
storage/csv/ha_tina.cc:
  Found that if we don't bzero handlerton, that things can go boom!
  
  This probably needs to be fixed for all handlers

sql/mysqld.cc

@@ -357,9 +357,7 @@ my_bool opt_show_slave_auth_info, opt_sql_bin_update = 0;
 my_bool opt_log_slave_updates= 0;
 my_bool	opt_innodb;
 #ifdef WITH_INNOBASE_STORAGE_ENGINE
-extern uint innobase_init_flags, innobase_lock_type;
-extern uint innobase_flush_log_at_trx_commit;
-extern ulong innobase_cache_size, innobase_fast_shutdown;
+extern ulong innobase_fast_shutdown;
 extern ulong innobase_large_page_size;
 extern char *innobase_home, *innobase_tmpdir, *innobase_logdir;
 extern long innobase_lock_scan_time;
@@ -383,11 +381,6 @@ extern my_bool innobase_log_archive,
                innobase_use_native_aio,
                innobase_file_per_table, innobase_locks_unsafe_for_binlog,
                innobase_create_status_file;
-extern my_bool innobase_very_fast_shutdown; /* set this to 1 just before
-                                            calling innobase_end() if you want
-                                            InnoDB to shut down without
-                                            flushing the buffer pool: this
-                                            is equivalent to a 'crash' */
 extern "C" {
 extern ulong srv_max_buf_pool_modified_pct;
 extern ulong srv_max_purge_lag;