Use a single write txn
Remember oldest reader txnid

Don't walk the readers table unless we really need to.
More for me_pgoldest

Leave it in main env struct, it doesn't need to be rolled back
with nested txns.
Change retry to num times 60.  Testing shows that on a known dataset, this has the same growth behavior as 2.4.39, while num times 20 resulted in significant growth.
Merge remote-tracking branch 'origin/mdb.master'
Release 0.9.14
Merge remote-tracking branch 'origin/mdb.master'
Flesh out txn support

Only in back-mdb; back-bdb needs work but it's deprecated;
not worth the effort. In particular txn, retry after deadlocks
makes the whole thing too messy.
Add updateControls to txn response
Consolidate LDAP_TXN precheck

This commit was accidentally omitted from previous push
LDAP_TXN is now RFC 5805
Silence some clang warnings
ITS#7941 fix for repeated tags

Make sure ntags isn't incremented if we're skippnig the tag
Plug leak in 4d02c741b120786df1b87ee9ed49c1d3f9bc7522

Free writer txn on env_close
ITS#7942 plug leak in controls
Merge remote-tracking branch 'origin/mdb.master'
ITS#7942 tweak previous commit

Only free when cleaning up operation controls, not response controls.
(This only makes a difference on search requests, which may have
multiple responses with the same set of controls.)
ITS#7943 reinit txn flags

When reusing the main write txn
Merge remote-tracking branch 'origin/mdb.master'
Fix mdb_txn cleanup