Coding style: classes start with a capital letter.
Rename some classes related to parsing:
create_field -> Create_field
foreign_key -> Foreign_key
key_part_spec -> Key_part_spec


sql/field.cc:
  create_field -> Create_field
sql/field.h:
  create_field -> Create_field
sql/item.h:
  create_field -> Create_field
sql/item_sum.cc:
  create_field -> Create_field
sql/mysql_priv.h:
  create_field -> Create_field
sql/sp_head.cc:
  create_field -> Create_field
sql/sp_head.h:
  create_field -> Create_field
sql/sp_pcontext.cc:
  create_field -> Create_field
sql/sp_pcontext.h:
  create_field -> Create_field
sql/sp_rcontext.cc:
  create_field -> Create_field
sql/sql_class.cc:
  create_field -> Create_field
  key_part_spec -> Key_part_spec
  foreign_key -> Foreign_key
sql/sql_class.h:
  create_field -> Create_field
  key_part_spec -> Key_part_spec
  foreign_key -> Foreign_key
sql/sql_insert.cc:
  create_field -> Create_field
sql/sql_lex.cc:
  Coding style: classes start with a capital, create_field -> Create_field
sql/sql_lex.h:
  create_field -> Create_field
  key_part_spec -> Key_part_spec
sql/sql_parse.cc:
  create_field -> Create_field
  key_part_spec -> Key_part_spec
sql/sql_select.cc:
  create_field -> Create_field
sql/sql_table.cc:
  create_field -> Create_field
sql/sql_yacc.yy:
  create_field -> Create_field
  key_part_spec -> Key_part_spec
  foreign_key -> Foreign_key
sql/unireg.cc:
  create_field -> Create_field