myisam/mi_uniue.c:mi_check_unique() should skip trailing spaces comparing 
TEXT and VARTTEXT key segments.


myisam/mi_unique.c:
  Fix for bug #20709: Collation not used in group by on 4.1.    
  
  myisam/mi_uniue.c:mi_check_unique() should skip trailing spaces comparing 
  TEXT and VARTTEXT key segments.
    
  Example: assume, we have a 'char(200) collate utf8_unicode_ci' field,
  there are two records with _utf8"0x65" and _utf8"0xC3A9" characters;
  these values are equal according
  to the utf8_unicode_ci collation, but two 600 byte length corresponding keys:  
  "0x65<0x20 repeats 599 times>" and "0xC3A9<0x20 repeats 598 times>" are not    
  equal if we count trailing spaces and it may cause inconsequent behavior.
  
  So, let's pass 1 as the skip_end_space parameter value to the mi_compare_text()
  function for proper TEXT and VARTTEXT key segments comparison.
mysql-test/r/ctype_utf8.result:
  Fix for bug #20709: Collation not used in group by on 4.1.    
    - test results.
mysql-test/t/ctype_utf8.test:
  Fix for bug #20709: Collation not used in group by on 4.1.    
    - test case.