Don't display charsets/collations with HIDDEN flag.
ctype-utf8.c:
  Adding HIDDEN flag to "filename"
  Changeing ID to 17 which was previosly
  used by deprecated "win1251", removed in 4.1.
charset-def.c:
  Adding "filename" as a hidden charset, for test purposes.
m_ctype.h:
  Adding MY_CS_HIDDEN flag,
  to hide charsets and collations from
  being displayed in SHOW.