Select from a view with the underlying HAVING clause failed with a
message: "1356: View '...' references invalid table(s) or column(s)
or function(s) or definer/invoker of view lack rights to use them"

The bug is a regression of the fix for bug 11750328 - 40825 (similar
case, but the HAVING cause references an aliased field).
In the old fix for bug 40825 the Item_field::name_length value has
been used in place of the real length of Item_field::name. However,
in some cases Item_field::name_length is not in sync with the
actual name length (TODO: combine name and name_length into a
solid String field).

The Item_ref::print() method has been modified to calculate actual
name length every time.


mysql-test/r/view.result:
  Test case for bug #11829681
mysql-test/t/view.test:
  Test case for bug #11829681
sql/item.cc:
  Bug #11829681 - 60295: ERROR 1356 ON VIEW THAT EXECUTES FINE AS A QUERY
  
  The Item_ref::print() method has been modified to calculate actual
  name length every time.
sql/item.h:
  Minor commentary.