SQL-mode PAD_CHAR_TO_FULL_LENGTH affected mysqld's user-table too. If
enabled, user-name and host were space-padded and no longer matched
the login-data of incoming connexions.

Patch disregards pad-flag while loading privileges so ability to log
in does not depend on SQL-mode.


mysql-test/r/sql_mode.result:
  show that SQL-mode 'PAD_CHAR_TO_FULL_LENGTH' does not affect
  loading of privileges (and by extension, ability to log in).
mysql-test/t/sql_mode.test:
  show that SQL-mode 'PAD_CHAR_TO_FULL_LENGTH' does not affect
  loading of privileges (and by extension, ability to log in).
sql/sql_acl.cc:
  temporarily disable SQL-mode 'PAD_CHAR_TO_FULL_LENGTH' while
  reloading privileges