Minor fix to previous code

sql/mysql_priv.h:
  Add ifdef to allow compilation without Innodb

sql/mysql_priv.h

@@ -657,7 +657,10 @@ extern ulong binlog_cache_size, max_binlog_cache_size, open_files_limit;
 extern ulong max_binlog_size, rpl_recovery_rank, thread_cache_size;
 extern ulong com_stat[(uint) SQLCOM_END], com_other, back_log;
 extern ulong specialflag, current_pid;
+
+#ifdef HAVE_INNOBASE_DB
 extern ulong srv_max_buf_pool_modified_pct;
+#endif
 
 extern uint test_flags,select_errors,ha_open_options;
 extern uint protocol_version,dropping_tables;