myisam/mi_close.c:
  yet another generalization for rec_buff handling
myisam/mi_dynrec.c:
  yet another generalization for rec_buff handling
myisam/mi_extra.c:
  yet another generalization for rec_buff handling
myisam/mi_open.c:
  yet another generalization for rec_buff handling
myisam/myisamdef.h:
  yet another generalization for rec_buff handling