Fixed that --extern works with mysql-test-run.pl
Small trivial cleanups


include/my_global.h:
  Fixed unsafe define of uint4korr()
mysql-test/lib/mtr_report.pl:
  Removed wrong messages when using --extern
mysql-test/mysql-test-run.pl:
  Fixed that --extern works
  Print help on stdout instead of stderr (make it easier to pipe it to less)
mysql-test/t/ndb_lock.test:
  Added other possible error code
sql/sql_prepare.cc:
  Removed not needed casts