'#ifdef MDB_DEVEL' -> '#if MDB_DEVEL'
Fix comments, use actual PAGEBASE macro as originally intended.
Actually enable 64K pages. Set MDB_DATA_VERSION for testing only.

mdb_txn_commit(child): Give loose pages to parent.
Use a pointer beyond the page header instead of mp_next, so
we will not need to save/restore mp_pgno. This avoids a crash
caused by references to mp_pgno.

Fix in 534dcc72 was in wrong place

Fix mp_lower/mp_upper to exclude PAGEHDRSZ, which means our
max mp_upper is now pagesize - PAGEHDRSZ and won't overflow.
Currently must define MDB_DEVEL to use. Will be default for
LMDB 1.0/OpenLDAP 2.5

Use gcc section attribute to keep less frequently used functions
away from main code.

Make sure the writer thread starts and stops when we expect it to.

Due to 89bae499

And mdb_env_copyfd2(). Perform compaction on the copy. Trims out
freed pages and renumbers data pages in sequential order. This is
more CPU-intensive since it copies and modifies data pages.

Ryan Tandy authored Jun 27, 2014 and Howard Chu committed Jun 30, 2014

Similar to #7858, another easy patch.

Don't try to write past end of file

MDB is the name of the backend, LMDB is the name of the DB engine.
Also update some BerkeleyDB info.

Do not overwrite loose pages' mp_pgno with mp_next.
mdb_page_flush() will use mp_pgno to rebuild dirty_list.

Try to exit cleanly to avoid leaving stale readers. Not
a critical issue since mdb_reader_check can take care of
them, but still cleaner.