We must use the db key length in sp_drop_db_routines (and not the
  number of characters), or long db names will be truncated in the key.


mysql-test/r/sp.result:
  Updated results for new test case (BUG#18344)
mysql-test/t/sp.test:
  Added new test case for BUG#18344.
sql/sp.cc:
  In sp_drop_db_routines(), give the key field's ("db") key length
  instead of the number of characters to index_read(), or the key
  packing will truncate long db names.