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.