Added new tests for better coverage of
  min/max optimization code.
func_group.test:
  Added new tests for better coverage of 
  min/max optimization code.
opt_sum.cc:
  Fixed wrong previous manual merge.
  Fixed bugs concerning fields used in min/max
  functions for which there are conditions of
  the form field=const.


sql/opt_sum.cc:
  Fixed wrong previous manual merge.
  Fixed bugs concerning fields used in min/max
  functions for which there are conditions of
  the form field=const.
mysql-test/t/func_group.test:
  Added new test for better coverage of 
  min/max optimization code.
mysql-test/r/func_group.result:
  Added new tests for better coverage of
  min/max optimization code.