fix mysql_change_user() for old clients


include/mysql_com.h:
  Mover global defines here
libmysql/libmysql.c:
  Remove end spaces from all lines
scripts/mysql_fix_privilege_tables.sh:
  Move password modification to separate alter table
sql/mini_client.cc:
  Defines, fold long lines
sql/mysqld.cc:
  Backup old scramble for mysql_change_user to work from old clients
sql/password.c:
  Several minor optimizations
sql/sql_acl.cc:
  Remove ending spaces
sql/sql_class.h:
  Add old scramble for mysql_change_user to work with old clients
sql/sql_parse.cc:
  Remove end spaces.