Merge with 3.23 to get fixes for --user and BACKUP TABLE

BitKeeper/etc/ignore:
  auto-union
BitKeeper/deleted/.del-delete.result:
  Delete: mysql-test/r/delete.result
BitKeeper/deleted/.del-stamp-h.in~4a5d6676232516c5:
  Auto merged
client/mysqlbinlog.cc:
  Auto merged
include/my_sys.h:
  Auto merged
libmysql/libmysql.c:
  Auto merged
mysql-test/t/delete.test:
  Auto merged
mysql-test/t/join.test:
  Auto merged
mysql-test/t/type_datetime.test:
  Auto merged
mysys/my_copy.c:
  Auto merged
sql/field.h:
  Auto merged
sql/opt_range.cc:
  Auto merged
sql/share/polish/errmsg.txt:
  Auto merged
sql/sql_rename.cc:
  Auto merged
sql/sql_select.cc:
  Auto merged
mysql-test/mysql-test-run.sh:
  merge with 3.23.56
mysql-test/r/backup.result:
  merge (needs to be updated)
mysql-test/r/join.result:
  merge (needs to be updated)
mysql-test/r/type_datetime.result:
  merge (needs to be updated)
mysql-test/t/backup.test:
  merge with 3.23
scripts/mysqld_safe.sh:
  Only use first --user option
sql/ha_myisam.cc:
  Don't let BACKUP TABLE overwrite old files
sql/log_event.h:
  merge
sql/mysql_priv.h:
  merge
sql/mysqld.cc:
  Use first --user option
sql/slave.cc:
  use local version
sql/sql_repl.h:
  use local version

scripts/mysqld_safe.sh

@@ -38,7 +38,12 @@ parse_arguments() {
       --basedir=*) MY_BASEDIR_VERSION=`echo "$arg" | sed -e "s;--basedir=;;"` ;;
       --datadir=*) DATADIR=`echo "$arg" | sed -e "s;--datadir=;;"` ;;
       --pid-file=*) pid_file=`echo "$arg" | sed -e "s;--pid-file=;;"` ;;
-      --user=*)    user=`echo "$arg" | sed -e "s;--[^=]*=;;"` ; SET_USER=1 ;;
+      --user=*)
+        if [ $SET_USER == 0 ]
+	then
+          user=`echo "$arg" | sed -e "s;--[^=]*=;;"` ; SET_USER=1
+        fi
+        ;;
 
       # these two might have been set in a [mysqld_safe] section of my.cnf
       # they get passed via environment variables to mysqld_safe