mysql-test/r/func_gconcat.result:
  result fixed
mysql-test/r/subselect.result:
  result fixed
mysql-test/r/type_float.result:
  result fixed
mysql-test/t/type_float.test:
  testcase added
sql/item_func.cc:
  Now we set decimals to NOT_FIXED_DEC if the max_length is longer than
  maximum possible double length