(MySQL plugin interface: status variables)

adding SHOW_FUNC, removing SHOW_some_specific_value,
only generic SHOW_LONG/SHOW_CHAR/etc are recognized.
changing to use SHOW_FUNC instead of ha_update_statistics


sql/ha_innodb.h:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  removing ha_update_statistics().
sql/handler.cc:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  removing ha_update_statistics().
sql/handler.h:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  removing ha_update_statistics().
sql/mysqld.cc:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  adding SHOW_FUNC, removing SHOW_some_specific_variable,
  only generic SHOW_LONG/SHOW_CHAR/etc are recognized.
  changing to use SHOW_FUNC instead of ha_update_statistics
sql/set_var.cc:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  adding SHOW_FUNC, removing SHOW_some_specific_variable,
  only generic SHOW_LONG/SHOW_CHAR/etc are recognized.
sql/sql_show.cc:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  adding SHOW_FUNC, removing SHOW_some_specific_variable,
  only generic SHOW_LONG/SHOW_CHAR/etc are recognized.
  changing to use SHOW_FUNC instead of ha_update_statistics
sql/structs.h:
  cleanup of SHOW STATUS code, as a preparation for WL#2935
  adding SHOW_FUNC, removing SHOW_some_specific_variable,
  only generic SHOW_LONG/SHOW_CHAR/etc are recognized.