note: this does *not* move pagecache* variables.


sql/mysqld.cc:
  remove maria_* variables from the server, declare them in ha_maria.cc
sql/set_var.cc:
  remove maria_* variables from the server, declare them in ha_maria.cc
sql/sql_class.h:
  remove maria_* variables from the server, declare them in ha_maria.cc
sql/sql_plugin.cc:
  bugfix: support for ENUM/SET thd local plugin variables
storage/maria/ha_maria.cc:
  remove maria_* variables from the server, declare them in ha_maria.cc