The patch adds DYNAMIC_ARRAY all_status_vars, which is now the
sole source of status information for SHOW STATUS. Status
variables can be added to and removed from the array dynamically.
SHOW STATUS command uses this array instead of static array
from mysqld.cc
Compatibility with the old, global list of status variables is
preserved in init_server_components(), where this global list is
simply appended to all_status_vars.
is the same in the plugin and in the mysqld.
store the size in the plugin.
To simplify access to plugin's st_mysql_plugin, copy it on open and
convert to the latest version, so that the rest of the code would
not need to care about versions.
