Merge some merge changesets from 5.0 up into 5.1-build

(code changes have already been merged separately).

Use this occasion to fix the branch name in the configuration file.

.bzr-mysql/default.conf

 [MYSQL]
 post_commit_to = "commits@lists.mysql.com"
 post_push_to = "commits@lists.mysql.com"
-tree_name = "mysql-5.1-bugteam"
+tree_name = "mysql-5.1"