- Addressing review feedback, generation 4.

include/my_global.h:
  Make ALIGN_PTR's action correspond to that of ALIGN_SIZE
sql/item.cc:
  MWL#17: Table-elimination
  - Review feedback: function renames, better comments
sql/item.h:
  MWL#17: Table-elimination
  - Review feedback: function renames, better comments
sql/item_cmpfunc.cc:
  MWL#17: Table-elimination
  - Review feedback: function renames, better comments
sql/item_subselect.cc:
  MWL#17: Table-elimination
  - Review feedback: function renames, better comments
sql/item_subselect.h:
  MWL#17: Table-elimination
  - Review feedback: function renames, better comments
sql/opt_table_elimination.cc:
  MWL#17: Table-elimination
  - Addressing review feedback, generation 4: abstract everything in case
    we would need to change it for something else in the future.
sql/sql_list.h:
  MWL#17: Table-elimination
  - Introduce exchange_sort(List<T> ...) template function
sql/sql_select.cc:
  MWL#17: Table-elimination
  - Review feedback: function renames, better comments