Added key cache parameters for midpoint insertion strategy
Many files:
  Added midpoint insertion strategy for key cache
mi_test2.c:
  Added a parameter to resize_key_cache


mysys/mf_keycache.c:
  Added midpoint insertion strategy for key cache
myisam/mi_check.c:
  Added midpoint insertion strategy for key cache
myisam/mi_page.c:
  Added midpoint insertion strategy for key cache
myisam/mi_range.c:
  Added midpoint insertion strategy for key cache
myisam/rt_index.c:
  Added midpoint insertion strategy for key cache
myisam/rt_split.c:
  Added midpoint insertion strategy for key cache
myisam/mi_delete.c:
  Added midpoint insertion strategy for key cache
myisam/mi_preload.c:
  Added midpoint insertion strategy for key cache
myisam/mi_search.c:
  Added midpoint insertion strategy for key cache
myisam/mi_write.c:
  Added midpoint insertion strategy for key cache
myisam/rt_key.c:
  Added midpoint insertion strategy for key cache
myisam/mi_test2.c:
  Added a parameter to resize_key_cache
isam/_page.c:
  Added midpoint insertion strategy for key cache
include/my_sys.h:
  Added midpoint insertion strategy for key cache
myisam/myisamdef.h:
  Added midpoint insertion strategy for key cache
sql/handler.h:
  Added key cache parameters for midpoint insertion strategy.
sql/set_var.h:
  Added key cache parameters for midpoint insertion strategy.
sql/handler.cc:
  Added key cache parameters for midpoint insertion strategy.
sql/mysqld.cc:
  Added key cache parameters for midpoint insertion strategy.
sql/set_var.cc:
  Added key cache parameters for midpoint insertion strategy.