Remove deprecated value 63 for this switch, and the old function find_best()
that was controlled by this value.
 
mysql-test/r/greedy_optimizer.result
  WL#5369: Updated test result.

mysql-test/r/mysqld--help-notwin.result
  WL#5369: Updated test result.

mysql-test/r/mysqld--help-win.result
  WL#5369: Updated test result.

mysql-test/suite/sys_vars/r/optimizer_search_depth_basic.result
  WL#5369: Updated test result.

mysql-test/suite/sys_vars/t/optimizer_search_depth_basic.test
  WL#5369: Updated test file.

mysql-test/t/greedy_optimizer.test
  WL#5369: Updated test file.

sql/sql_select.cc
  Removed test for 'MAX_TABLES+2' in choose_plan(), removed function
  find_best(), ie we are now always calling greedy_search(), unless we
  use straight_join to override the join optimizer.

sql/sql_select.h
  Removed reference to find_best().

sql/sys_vars.cc
  Updated limits and comment for variable optimizer-search-depth.