The length of the prefix of the pattern string in the LIKE predicate that 
determined the index range to be scanned was calculated incorrectly for
multi-byte character sets. 
As a result of this in 4. 1 the the scanned range was wider then necessary
if the prefix contained not only one-byte characters.  
In 5.0 additionally it caused missing some rows from the result set.


mysql-test/r/ctype_utf8.result:
  Added test cases for bug #16674.
mysql-test/t/ctype_utf8.test:
  Added test cases for bug #16674.
strings/ctype-mb.c:
  Fixed bug #16674.
  The length of the prefix of the pattern string in the LIKE predicate that 
  determined the index range to be scanned was calculated incorrectly for
  multi-byte character sets. 
  As a result of this in 4. 1 the the scanned range was wider then necessary
  if the prefix contained not only one-byte characters.  
  In 5.0 additionally it caused missing some rows from the result set.
      
  The function my_like_range_mb was fixed to calculate the length of
  the prefix in a pattern string correctly in all cases.