argument can lead to a wrong result.

md5() and sha() functions treat their arguments as case sensitive strings.
But when they are compared their arguments were compared as a case
insensitive strings which leads to two functions with different arguments
and thus different results to being identical. This can lead to a wrong
decision made in the range optimizer and thus lead to a wrong result set.

Item_func_md5::fix_length_and_dec() and Item_func_sha::fix_length_and_dec()
functions now set binary collation on their arguments.


sql/item_strfunc.cc:
  Fixed bug#15351: Wrong collation used for comparison of md5() and sha()
  argument can lead to a wrong result.
  Item_func_md5::fix_length_and_dec() and Item_func_sha::fix_length_and_dec()
  functions now set binary collation on their arguments.
mysql-test/r/func_str.result:
   Added test case for the bug#15351: Wrong collation used for comparison of md5() and sha()
  argument can lead to a wrong result.
mysql-test/t/func_str.test:
  Added test case for the bug#15351: Wrong collation used for comparison of md5() and sha()
  argument can lead to a wrong result.