Add second shortener to create_index_name for very long columns

import hashlib

from django.db.backends.creation import BaseDatabaseCreation

from django.db.backends.util import truncate_name

from django.utils.log import getLogger

        if len(index_name) > self.connection.features.max_index_name_length:

            part = ('_%s%s%s' % (column_names[0], index_unique_name, suffix))

            index_name = '%s%s' % (table_name[:(self.connection.features.max_index_name_length - len(part))], part)

        # If it's STILL too long, just hash it down

        if len(index_name) > self.connection.features.max_index_name_length:

            index_name = hashlib.md5(index_name).hexdigest()[:self.connection.features.max_index_name_length]

        return index_name

    def _constraint_names(self, model, column_names=None, unique=None, primary_key=None, index=None, foreign_key=None, check=None):