NAMES.

Issue here is, stored routines, events and resource group names
are case and accent insensitive. While creating MDL_key and
data-dictionary cache keys, only case sensitiveness is considered
but not the accent sensitiveness for these object names. Hence
key comparison of accent insensitive name yielded the wrong
result and hit the asserts mentioned in the bug report.

While creating MDL_key and DD cache key, currently the case
is stripped off by lower casing the names. But for key comparisons
to yield correct result, even the accent should be stripped off
from the names.

So to fix this issue, while creating keys for MDL and DD cache
the object names are normalized (to strip off both case and accent).
The normalized name contains weights of each character of the
name (strnxfrm() of collation is used to normalize the name).
utf8_general_ci collation is used by these objects and normalized
name contains two byte value for each character with the
utf8_general_ci collation. The normalized name is used in the
comparison and it yields the expected result.

MDL_key with normalized object name:

  MDL_key::mdl_key_init() is overloaded to accept the normalized
  object name and form a key with a quadruplet

   @<mdl_namespace@>+@<database name@>+@<normalized object name@>+
                                              @<object name@>

  For key compare operations, key length only till end of
  normalized object name is used.

  Object name in the MDL_key is used by the performance_schema
  for metadata locks listing. Similar to MDL_key from for columns,
  object name is stored only if there is sufficient space.
  Not listing a object name from the performance schema when
  there is no space should be OK instead of increasing the MDL_key
  size to store full object name.

DD cache key with normalized object name:

  DD Global_name_key, Item_name_key and Routine_name_key class's
  operator<() is updated to compare object names using my_strnncoll().
  New static method name_collation() in dd::tables::* classes gets the
  collation used for the name field. Same collation is used with
  my_strnncoll() to yield the correct results.

  TODO: Object_table_definition_impl::name_collation() is implemented
        as a static function now.
        Changing name collation is not supported during upgrade now.
        To support this, static definition of this method should be
        avoided and should provide a possibility to have different
        collations for actual and target table definition.

Sroutine_has_entry with normalized routine object name:

  The key for the Sroutine_has_entry hash is modified to hold the
  normalized names for the stored routines now. Binary comparison
  of routine keys yield the correct results.

Change-Id: I70276c4128422168ba81c9d5e28efe8d80244d9b