Move handling of suffix_length from strnxfrm_bin() to filesort to ensure proper sorting of all kind of binary objects
field::sort_key() now adds length last for varbinary/blob
VARBINARY/BLOB is now sorted by filesort so that shorter strings comes before longer ones
Fixed issues in test cases from last merge



mysql-test/r/select.result:
  Change column name in test to get GROUP BY to use the alias
mysql-test/r/type_blob.result:
  Test BLOB and VARCHAR sorting
mysql-test/t/select.test:
  Change column name in test to get GROUP BY to use the alias
  Drop used tables at start of test
  Don't use table names 'a', 'b' or 'c'
mysql-test/t/type_blob.test:
  Test BLOB and VARCHAR sorting
sql/field.cc:
  Store length last in VARBINARY() and BLOB() columns to get shorter strings sorted before longer onces
sql/field.h:
  Added method 'sort_length()' to allow one to have length bytes last for VARBINARY/BLOB to get these to sort properly
sql/filesort.cc:
  Use 'sort_length()' instead of 'pack_length()' to get length of field.
  Store suffix_length last for varbinary (blob) objects.
  The above ensures that BLOB/VARBINARY are correctly sorted (shorter strings before longer ones)
sql/sql_class.h:
  Added sort suffix length (to get varbinary/blob to sort correctly)
sql/sql_select.cc:
  Use sort_length() instead of pack_lengths()
strings/ctype-bin.c:
  Don't let strnxfrm_bin store length last
  Better to do it in MySQL field object to ensure it's done properly for all cases