Problem: After introducing of LC_TIME_NAMES variable,  the 
function date_format() can return international non-ascii
characters in month and weekday names. Thus, it cannot return
a binary string anymore, because inserting a result of date_format()
into a column with non-utf8 character set produces garbage.
Fix: date_format() now returns a character string, using
"collation_connection" to detect character set and collation
for the returned value. This allows to insert
results of date_format() properly into columns with
various character sets.


mysql-test/r/ctype_utf8.result:
  Adding test case.
  Fixing old result.
mysql-test/t/ctype_utf8.test:
  Adding test case.
sql/item_timefunc.cc:
  DATE_FORMAT() now returns a character string
  instead of binary string:
  - make_date_time() now converts localte data from UTF8 to 
  the character set of "str" argument, instead of copying as is.
  - fix_dec_and_length() now uses "collation_connection"
  instead of "binary" for the result, it also now
  multiplies to mbmaxlen when calculating max_length