Plugin should be able to specify status variables that are shown in SHOW STATUS
st_plugin has a field for an array of variables, when plugin is installed, this array is added to the list of variables in the pluginname_ namespace (see how innodb status variables are added now) st_plugin also has a field for a function that is called before these variables are accessed. even better would be to add newe status variable type - a function. This function returns variable type and variable data. this way we eliminate innodb_update_status, and plugin's function mentioned above. instead innodb_update_status goes directly into status variable array and returns variable array that is stored there now. Having this function status type, we should remove all "specific" status types, like SHOW_UPTIME, etc. and only keep generic SHOW_STR, SHOW_LONG, and so on. show status types should describe the representation of the data, not the semantics.