new file
Many files:
  Added CACHE INDEX command


sql/ha_myisam.cc:
  Added CACHE INDEX command
sql/handler.cc:
  Added CACHE INDEX command
sql/sql_lex.cc:
  Added CACHE INDEX command
sql/sql_parse.cc:
  Added CACHE INDEX command
sql/sql_table.cc:
  Added CACHE INDEX command
sql/ha_myisam.h:
  Added CACHE INDEX command
sql/handler.h:
  Added CACHE INDEX command
sql/mysql_priv.h:
  Added CACHE INDEX command
sql/sql_lex.h:
  Added CACHE INDEX command
sql/sql_yacc.yy:
  Added CACHE INDEX command