After merge fix.


include/keycache.h:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Status variables moved into KEY_CACHE in 4.1.
  Enlarging them there.
include/my_sys.h:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Status variables moved into KEY_CACHE in 4.1.
  Removed unused global variables.
myisam/mi_test2.c:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Status variables moved into KEY_CACHE in 4.1.
  Changed to print default key cache status.
mysys/mf_keycache.c:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Status variables moved into KEY_CACHE in 4.1.
  Changed their debug printout.
sql/mysqld.cc:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Changed to print full value.
sql/sql_show.cc:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Added a branch for long long values.
sql/sql_test.cc:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  changed to print full values.
sql/structs.h:
  Bug#12920 - key_read_requests counter appears to re-set
  After merge fix.
  Added a branch for long long keycache values.