Problem: when inserting supplementary characters to an UCS2 column,
character was silently shrinked to 16-bit value.

Fix: produce a warning on attempt to insert a supplementary character,
and convert to question mark.

  @ mysql-test/r/ctype_many.result
  @ mysql-test/t/ctype_many.test
  Adding tests

  @ strings/ctype-ucs2.c
  Check if wc is greater than the highest value supported (0xFFFF),
  return MY_CS_ILUNI if true.